bluuebunny/crossref_metadata_2025 huggingface dataset:
A framework for combining multiple soil moisture retrievals based on maximizing temporal correlation
Authors: Kim Seokhyeon , Parinussa Robert M. , Liu Yi. Y. , Johnson Fiona M. , Sharma Ashish
Published: July 2015

A method for combining two microwave satellite soil moisture products by maximizing the temporal correlation with a reference data set has been developed. The method was applied to two global soil moisture data sets, Japan Aerospace Exploration Agency (JAXA) and Land Parameter Retrieval Model (LPRM), retrieved from the Advanced Microwave Scanning Radiometer 2 observations for the period 2012–2014. A global comparison revealed superior results of the combined product compared to the individual products against the reference data set of ERA‐Interim volumetric water content. The global mean temporal correlation coefficient of the combined product with this reference was 0.52 which outperforms the individual JAXA (0.35) as well as the LPRM (0.45) product. Additionally, the performance was evaluated against in situ observations from the International Soil Moisture Network. The combined data set showed a significant improvement in temporal correlation coefficients in the validation compared to JAXA and minor improvements for the LPRM product.
Seasonal variation of the upper ocean responding to surface heating in the North Pacific
Authors: Lee Eunjeong , Noh Yign , Qiu Bo , Yeh Sang‐Wook
Published: July 2015

Seasonal variations of the upper ocean, such as mixed layer depth (MLD) and sea surface temperature (SST), responding to the atmospheric forcing in the North Pacific (10°N–50°N), are investigated by analyzing the Argo and NCEP/NCAR reanalysis 1 data. The OAFlux data are also used for comparison. During the early heating period in the high‐latitude ocean north of 30°N, where a seasonal thermocline is formed above the deep mixed layer under strong surface heating, the MLD h is found to be scaled as
, where L is the Monin‐Obukhov length scale and λ is the Ekman length scale. On the other hand, in the low‐latitude ocean south of 30°N, where the preexisting MLD is shallow and surface heating is weak, h is found to be scaled by λ. It is found that a large amount of heat flux across the MLD occurs, especially in the high‐latitude ocean during the late heating period, in which h is small. It suggests the contribution by turbulent mixing across the MLD in addition to radiation penetration, and the eddy diffusivity in the high‐latitude ocean is estimated as
∼ 10−4−10−3 m2 s−1. The heat budget of the mixed layer reveals that the contribution from the ocean heat transport is much smaller than the surface heat flux in the high‐latitude ocean except in the Kuroshio region, but it is sometimes comparable in the low‐latitude ocean.
Coupled dynamics of interfacial waves and bed forms in fluid muds over erodible seabeds in oscillatory flows
Authors: Trowbridge J. H. , Traykovski P.
Published: July 2015

Recent field investigations of the damping of ocean surface waves over fluid muds have revealed waves on the interface between the thin layer of fluid mud and the overlying much thicker column of clear water, accompanied by bed forms on the erodible seabed beneath the fluid mud. The frequencies and wavelengths of the observed interfacial waves are qualitatively consistent with the linear dispersion relationship for long interfacial waves, but the forcing mechanism is not known. To understand the forcing, a linear model is proposed, based on the layer‐averaged hydrostatic equations for the fluid mud, together with the Meyer‐Peter‐Mueller equation for the sediment transport within the underlying seabed, both subject to oscillatory forcing by the surface waves. If the underlying seabed is nonerodible and flat, the model indicates parametric instability to interfacial waves, but the threshold for instability is not met by the observations. If the underlying seabed is erodible, the model indicates that perturbations to the seabed elevation in the presence of the oscillatory forcing create interfacial waves, which in turn produce stresses within the fluid mud that force a net transport of sediment within the seabed toward the bed form crests, thus causing growth of both bed forms and interfacial waves. The frequencies, wavelengths, and growth rates are in qualitative agreement with the observations. A competition between mixing created by the interfacial waves and gravitational settling might control the thickness, density, and viscosity of the fluid muds during periods of strong forcing.
Indirect evidence for substantial damping of low‐mode internal tides in the open ocean
Authors: Ansong Joseph K. , Arbic Brian K. , Buijsman Maarten C. , Richman James G. , Shriver Jay F. , Wallcraft Alan J.
Published: July 2015

A global high‐resolution ocean circulation model forced by atmospheric fields and the M2 tidal constituent is used to explore plausible scenarios for the damping of low‐mode internal tides. The plausibility of different damping scenarios is tested by comparing the modeled barotropic tides with TPXO8, a highly accurate satellite‐altimetry‐constrained tide model, and by comparing the modeled coherent baroclinic tide amplitudes against along‐track altimetry. Five scenarios are tested: (1) a topographic internal wave drag, argued here to represent the breaking of unresolved high vertical modes, applied to the bottom flow (default configuration), (2) a wave drag applied to the barotropic flow, (3) absence of wave drag, (4) a substantial increase in quadratic bottom friction along the continental shelves (with wave drag turned off), and (5) application of wave drag to the barotropic flow at the same time that quadratic bottom friction is substantially increased along the shelves. Of the scenarios tested here, the default configuration (1) yields the most accurate tides. In all other scenarios (2–5), the lack of damping on open ocean baroclinic motions yields baroclinic tides that are too energetic and travel too far from their sources, despite the presence of a vigorous mesoscale eddy field which can scatter and decohere internal tides in the model. The barotropic tides are also less accurate in the absence of an open ocean damping on barotropic motions, that is, in scenarios (3) and (4). The results presented here suggest that low‐mode internal tides experience substantial damping in the open ocean.
The interaction between the tropopause inversion layer and the inertial gravity wave activities revealed by radiosonde observations at a midlatitude station
Authors: Zhang Yehui , Zhang Shaodong , Huang Chunming , Huang Kaiming , Gong Yun , Gan Quan
Published: July 2015

The interaction between the tropopause inversion layer (TIL) and the inertial gravity wave (IGW) activities is first presented by using a high vertical resolution radiosonde data set at a midlatitude station, Boise, Idaho (43.57°N, 116.22°W), for the period 1998–2008. The tropopause‐based vertical coordinate is used for the TIL detection, and for meticulously studying the IGW variation around the TIL, the broad spectral method is used for the IGW extraction. Generally, the TIL at the midlatitude station is stronger and thicker in winter and spring, which is consistent with previous studies. Our study confirmed the intense interaction between the TIL and IGW. It is found that the TIL not only could inhibit the upward propagation of IGWs from below but also imply the possible excitation links between the TIL and IGW. The results also indicate that the enhanced wind shear layer just 1 km above the tropopause may result in instability and finally leads to the IGW breaking and intensive turbulence. Subsequently, the IGW‐induced intensive turbulence leads to strong wave energy dissipation and a downward heat flux. This downward heat transportation could significantly cool the tropopause, while it has only negligible thermal effect on the atmosphere above the tropopause. Then, the IGW‐induced cooling at the tropopause makes the tropopause colder and sharper and finally forms the TIL. These suggest besides previously proposed mechanisms that IGWs also contribute greatly to the formation of TIL, which is consistent with a recent related simulation study.
Subseasonal variations in spatial signatures of ENSO on the Indian summer monsoon from 1901 to 2009
Authors: Gill Emily C. , Rajagopalan Balaji , Molnar Peter
Published: July 2015

Correlations of 1° by 1° seasonal rainfall with Pacific sea surface temperatures (SSTs) reveal spatially distinct teleconnections between El Niño–Southern Oscillation (ENSO) and Indian summer monsoon rainfall over the full monsoon season, as well as three subseasons. Over the full season (June–September), Pacific SSTs correlate with rainfall in Western India more than that in Eastern India. This spatial signature shifts as the monsoon progresses through early (June), middle or peak (July–August), and late (September) subseasons. Specifically, a 1°C cooling of the central equatorial Pacific (i.e., La Niña conditions) can result in the following: ∼70–100% increase in precipitation in north central Indian and the Indo‐Gangetic Plains during the early season, ∼30–80% increase peak season precipitation in south central India and northwestern Rajasthan, and ∼60–100% increase in late season precipitation in northern, northwestern, and central India. Furthermore, the spatial signatures between La Niña and El Niño are asymmetric in that for a particular location, the enhancement and suppression of rainfall associated with La Niña and El Niño conditions, respectively, are not equal. El Niño suppresses peak season rainfall in the south central and northwestern Rajasthan regions more than La Niña enhances it, but the opposite occurs during the late season in northern, northwestern, and central India. Additionally, the correspondence of minima (maxima) in anomalies of velocity potential aloft with maxima (minima) at 925 mb and with positive (negative) surface pressure anomalies suggests that anomalous subsidence (ascent) occurs in July–September during El Niño (La Niña) times. In the early season, however, patterns of velocity potential composites suggest a region of descent (ascent) over the western equatorial Indian Ocean, along with a region of ascent (descent) over the Indian subcontinent that exists only during the early season but not during the peak or late season. These patterns are consistent with the hypothesis that local Hadley cell circulation affects pressure and thus rainfall during the early season but that a larger‐scale mechanism, such as eastward or westward shifts in the Walker circulation, may be more responsible for teleconnections seen throughout the remainder of the season. These findings indicate that focusing monsoon forecasting efforts on these regions and on subseasonal periods while incorporating ENSO asymmetries will yield useful and skillful regional forecasts, compared to the declining utility and skill of all‐India summer monsoon rainfall.
Extended observations of polar mesosphere winter echoes over Andøya (69°N) using MAARSY
Authors: Latteck R. , Strelnikova I.
Published: July 2015

Continuous observations of Polar Mesosphere Winter Echoes (PMWE) have been conducted at the Norwegian island Andøya (69.30°N, 16.04°E) since autumn 2004 using the ALWIN VHF radar (until 2008) and the Middle Atmosphere Alomar Radar System (MAARSY) (since 2011). Using the more sensitive MAARSY compared to the ALWIN radar results in more detections characterized by smaller volume reflectivity values down to 4·10−18m−1 and a greater altitudinal coverage, 50–88 km compared to previous observations between 65 and 75 km. The results obtained by MAARSY show that the PMWE season starts clearly at the beginning of September with a mean seasonal occurrence rate of about 16%, but a strong seasonal variability with maxima up to 70% in the seasonal variation of the individual years. The end of the winter season is hard to determine since mesospheric echoes have also been observed below altitudes of 80km during nonwinter months, particularly around the end of May, i.e., the beginning of the polar mesospheric summer echo season, indicating that the physical mechanism for creating the lower mesospheric echoes is present during the early summer months as well.
The possible impact of urbanization on a heavy rainfall event in Beijing
Authors: Yu Miao , Liu Yimin
Published: July 2015

The impact of urbanization on a heavy rainfall event that occurred in Beijing on 21 July 2012 was investigated using version 3.6.1 of the Weather Research and Forecasting Model coupled with a multilayer urban canopy model. High‐resolution land use data for Beijing in 2010 with modified urban parameterization were introduced into the model. Evaluation showed that the simulation result generally agreed well with observations. Two sensitivity tests with different urban high‐resolution land use scenarios were employed to analyze the impact of urban expansion on this rainfall event. The simulation results confirmed that urbanization expansion played an important role in the distribution and intensity of precipitation for this extreme event. Urbanization led to total precipitation increasing in upstream and downstream directions. The start time of the precipitation process was advanced by 1 h, and the duration became longer due to the influence of urbanization. Moreover, urbanization caused the spatial distribution of precipitation to become more concentrated. The total precipitation amount above 250 mm and the frequency of precipitation intensity above 40 h−1 mm are both increased. The results of this study show that urbanization plays a significant role in frontal‐type rainfall.
A merging scheme for constructing daily precipitation analyses based on objective bias‐correction and error estimation techniques
Authors: Nie Suping , Luo Yong , Wu Tongwen , Shi Xueli , Wang Zaizhi
Published: July 2015

A new merging scheme (referred to as HL‐OI) was developed to combine daily precipitation data from high‐resolution gauge (HRG) observations, The Climate Prediction Center morphing technique (CMORPH) satellite estimates, and National Centers for Environmental Prediction (NCEP) numerical simulations over China to perform reliable high‐resolution daily precipitation analyses. The scheme is designed using a three‐step strategy of removing systemic biases, reducing random errors, quantitatively estimating error variances, and combining useful information from each data source. First, a cumulative distribution function matching procedure is adopted to reduce biases and provide unbiased background fields for the following merging processes. Second, the developed error estimation algorithm is implemented to quantify both the background and observation errors from the background departures. Third, the bias‐corrected NCEP and CMORPH data are combined with the HRG data using the optimal interpolation (OI) objective analysis technique. The magnitudes and spatial structures of both observation errors and background errors can be estimated successfully. Results of cross‐validation experiments show that the HL‐OI scheme effectively removes most of systemic biases and random errors in the background fields compared to the independent gauge observations and is robust even with imperfect background fields. The HL‐OI merging scheme significantly improves the temporal variations, agreements between the spatial patterns, frequency, and locations of daily precipitation occurrences. When information from gauge observations, satellite estimates, and model simulations are combined simultaneously, the merged multisource analyses perform better than dual‐source analyses. These results indicate that each independent information source of daily precipitation contributes to improving the quality of the final merged analyses under the framework of HL‐OI scheme.
Differences in pedotransfer functions of bulk density lead to high uncertainty in soil organic carbon estimation at regional scales: Evidence from Chinese terrestrial ecosystems
Authors: Xu L. , He N. P. , Yu G. R. , Wen D. , Gao Y. , He H. L.
Published: July 2015

Accurate estimation of soil organic carbon (SOC) storage is important for evaluating carbon sequestration of terrestrial ecosystems at regional scale. How the selected pedotransfer functions (PTFs) of bulk density (BD) influence the estimates of SOC storage is still unclear at large scales, although BD is an important parameter in all equations. Here we used data from the second national soil survey in China (8210 soil profiles) to evaluate the influence of eight selected PTFs on the estimation of SOC storage. The results showed that different PTFs may result in a higher uncertainty of SOC storage estimation and the coefficient of variation (CV, %) for the eight PTFs varied from 10.61% to 70.46% (mean = 12.75%). The observed CV values were higher in the 0–20 cm layer (12.48%) than in the 20–100 cm layer (10.05%). CV values were relatively stable (10–15%) when SOC content ranged from 0.13% to 3.45%. The findings indicate that PTFs may be used cautiously in soils with higher or lower SOC content. Estimates of SOC storage in the 0–100 cm soil layer varied from 67.19 to 95.97 Pg C in the eight PTFs in China, with an average of 87.36 ± 8.93 Pg C (CV = 10.23%). Our findings provide the insight that differences in PTFs are important sources of uncertainty in SOC estimates. The development of better PFTs, or the integration of various PFTs, is essential to accurately estimate SOC storage at regional scales.
The effects of hydrologic fluctuation and sulfate regeneration on mercury cycling in an experimental peatland
Authors: Coleman Wasik J. K. , Engstrom D. R. , Mitchell C. P. J. , Swain E. B. , Monson B. A. , Balogh S. J. , Jeremiason J. D. , Branfireun B. A. , Kolka R. K. , Almendinger J. E.
Published: July 2015

A series of severe droughts during the course of a long‐term, atmospheric sulfate‐deposition experiment in a boreal peatland in northern Minnesota created a unique opportunity to study how methylmercury (MeHg) production responds to drying and rewetting events in peatlands under variable levels of sulfate loading. Peat oxidation during extended dry periods mobilized sulfate, MeHg, and total mercury (HgT) to peatland pore waters during rewetting events. Pore water sulfate concentrations were inversely related to antecedent moisture conditions and proportional to past and current levels of atmospheric sulfate deposition. Severe drying events caused oxidative release of MeHg to pore waters and resulted in increased net MeHg production likely because available sulfate stimulated the activity of sulfate‐reducing bacteria, an important group of Hg‐methylating bacteria in peatlands. Rewetting events led to increased MeHg concentrations across the peatland, but concentrations were highest in peat receiving elevated atmospheric sulfate deposition. Dissolved HgT concentrations also increased in peatland pore waters following drought but were not affected by sulfate loading and did not appear to be directly controlled by dissolved organic carbon mobilization to peatland pore waters. Peatlands are often considered to be sinks for sulfate and HgT in the landscape and sources of MeHg. Hydrologic fluctuations not only serve to release previously sequestered sulfate and HgT from peatlands but may also increase the strength of peatlands as sources of MeHg to downstream aquatic systems, particularly in regions that have experienced elevated levels of atmospheric sulfate deposition.
Deformation of erosive and accretive forearcs during subduction of migrating and non‐migrating aseismic ridges: Results from 3‐D finite element models and application to the Central American, Peruvian, and Ryukyu margins
Authors: Zeumann Stefanie , Hampel Andrea
Published: July 2015

Subduction of aseismic oceanic ridges causes considerable uplift and deformation of the upper plate and may lead, for example, to the indentation of the forearc, the formation of marine terraces, or distinct fault patterns in the upper plate. Depending on the orientation of the ridge relative to the plate convergence direction, the ridge may either be stationary or migrate along the margin. Here we use three‐dimensional numerical models to investigate the tectonic evolution of forearcs affected by ridge subduction. In different experiments, we distinguish between migrating/non‐migrating ridges and accretive/erosive margins, respectively. Our results reveal that displacement and strain fields above migrating and non‐migrating ridges are asymmetric with respect to the ridge axis unless both ridge and plate convergence direction are perpendicular to the trench. As the asymmetric deformation pattern shifts along the margin through time, uplift caused by the underthrusting ridge is followed by subsidence when the ridge crest passed by, and regions initially experiencing shortening may subsequently undergo extension and vice versa. If the forearc comprises an accretionary prism, the ridge‐induced reentrant is larger than those in models with erosive forearcs and strain localizes in the frontal part of the wedge. Additional models with a setup adjusted to the Cocos and Gagua Ridges provide constraints on the onset of their subduction at the Central American and Ryukyu margins at ~2 Ma and 1 Ma, respectively. Displacement and strain fields from a model for the Nazca Ridge collision zone show good agreement with geological data from marine terraces and Quaternary faulting.
Aggression in US soldiers post‐deployment: Associations with combat exposure and PTSD and the moderating role of trait anger
Authors: Wilk Joshua E. , Quartana Phillip J. , Clarke‐Walper Kristina , Kok Brian C. , Riviere Lyndon A.
Published: July 2015

Anger and aggression are among the most common issues reported by returning service members from combat deployments. However, the pathways between combat exposure and anger and aggression have not been comprehensively characterized. The present study aimed to characterize the relationship between trait anger, combat exposure, post‐deployment PTSD, and aggression. U.S. Army soldiers (N = 2,420) were administered anonymous surveys assessing combat exposure, current PTSD symptoms and aggression, as well as trait anger items 3 months after returning from deployment to Afghanistan. PTSD symptom levels were related to aggression at higher levels of trait anger, but not evident among soldiers who had lower levels of trait anger. The pathway from combat exposure to PTSD, and then to aggression, was conditional upon levels of trait anger, such that the pathway was most evident at high levels of trait anger. This was the first study to our knowledge that concurrently modeled unconditional and conditional direct and indirect associations between combat exposure, PTSD, trait anger, and aggression. The findings can be helpful clinically and for developing screening protocols for combat exposed Soldiers. The results of this study suggest the importance of assessing and managing anger and aggression in soldiers returning from combat deployment. Anger is one of the most common complaints of returning soldiers and can have debilitating effects across all domains of functioning. It is imperative that future research efforts are directed toward understanding this phenomenon and developing and validating effective treatments for it. Aggr. Behav. 41:556–565, 2015. Published 2015. This article is a U.S. Government work and is in the public domain in the USA
Understanding the connection between self‐esteem and aggression: The mediating role of emotion dysregulation
Authors: Garofalo Carlo , Holden Christopher J. , Zeigler‐Hill Virgil , Velotti Patrizia
Published: July 2015

The purpose of the present study was to extend previous knowledge concerning the link between self‐esteem and aggression by examining the mediating role of emotion dysregulation among offenders and community participants. A sample of 153 incarcerated violent offenders and a community sample of 197 individuals completed self‐report measures of self‐esteem level, emotion dysregulation, and trait aggression. Offenders reported lower levels of self‐esteem than community participants, as well as greater levels of emotional nonacceptance and hostility. Bootstrapping analyses were performed to test whether emotion dysregulation mediated the association between self‐esteem level and aggression. In the offender sample, mediation models were significant for three of the four aspects of trait aggression that were considered. Emotion dysregulation fully mediated the links that low self‐esteem had with physical aggression, anger, and hostility. The same pattern (with the addition of full mediation for verbal aggression) was confirmed in the community sample. Our findings suggest that emotion dysregulation may play an important role in the connection between low self‐esteem and aggression. Alternative models of the associations among these variables were tested and discussed. As a whole, the present results are consistent with those of other studies and suggest that it may be beneficial to include emotion regulation modules as part of prevention and treatment programs for violent offenders. Aggr. Behav. 42:3–15, 2016. © 2015 Wiley Periodicals, Inc.
Precise Design of Phosphorescent Molecular Butterflies with Tunable Photoinduced Structural Change and Dual Emission
Authors: Zhou Chenkun , Tian Yu , Yuan Zhao , Han Mingu , Wang Jamie , Zhu Lei , Tameh Maliheh Shaban , Huang Chen , Ma Biwu
Published: July 2015

Photoinduced structural change (PSC) is a fundamental excited‐state dynamic process in chemical and biological systems. However, precise control of PSC processes is very challenging, owing to the lack of guidelines for designing excited‐state potential energy surfaces (PESs). A series of rationally designed butterfly‐like phosphorescent binuclear platinum complexes that undergo controlled PSC by Pt–Pt distance shortening and exhibit tunable dual (greenish‐blue and red) emission are herein reported. Based on the Bell–Evans–Polanyi principle, it is demonstrated how the energy barrier of the PSC, which can be described as a chemical‐reaction‐like process between the two energy minima on the first triplet excited‐state PES, can be controlled by synthetic means. These results reveal a simple method to engineer the dual emission of molecular systems by manipulating PES to control PSC.
Fully degradable antibacterial poly(ester‐phosphoester)s by ring‐opening polymerization, “click” chemistry, and quaternization
Authors: Yao Xuxia , Du Hong , Xu Ning , Sun Shuai , Zhu Weipu , Shen Zhiquan
Published: July 2015

Fully degradable cationic poly(ester‐phosphoester)s with antibacterial properties were prepared by a combination of ring‐opening polymerization (ROP) and “click” reaction. First, poly(ester‐phosphoester)s‐bearing alkynyl groups were synthesized by the ring‐opening copolymerization of 2‐(2‐propynyloxy)−2‐oxo‐1,3,2‐dioxaphospholane (propynyl ethylene phosphate, PEP) and ε‐caprolactone (CL) using lanthanum tris(2,6‐di‐tert‐butyl‐4‐methylphenolate)s (La(DBMP)3) as the catalyst. 2‐Azido‐N,N‐dimethylethanamine (DMEAN3) was then attached to the copolymers by “click” reaction, resulting in poly(ester‐phosphoester)s with pendant tertiary amines. After the quaternization reactions between the copolymer and various alkyl bromides, cationic poly(ester‐phosphoester)s containing ammonium groups were obtained. Optical density (OD) measurement shows that the cationic copolymers have excellent antibacterial activity, which makes them potential candidates as biomaterials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42647.
Thermoplastic softening behavior of organically modified polyoxotitanates: Effects of the amount of water and benzoylacetone for hydrolyzing alkoxides
Authors: Oda Shinya , Kozuka Hiromitsu , Uchiyama Hiroaki
Published: July 2015

Organically modified polyoxotitanates were prepared by hydrolyzing titanium tetra‐n‐butoxide in the presence of benzoylacetone (BzAc) in solution at Ti(OC4H9)4 : BzAc : H2O : CH3COCH3 mole ratios of 1 : (1 or 2) : (1 or 10) : 20. The solutions were concentrated at 80°C and dried at 140°C in N2 flow, producing transparent and yellow materials of BzAc‐modified polyoxotitanate. The materials had refractive indices of ∼1.7 and exhibited thermoplastic softening at temperatures below 70°C. Low contents of BzAc and high contents of H2O in solution led to higher softening temperatures of the materials, indicating the tunability of the softening temperature. Gel permeation chromatographic analyses showed that the higher softening temperatures originated mainly from polymerized species of higher molecular weights that were generated by hydrolysis and condensation reactions promoted by the low BzAc and high H2O contents in solution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42653.
Ethylene polymerization with homogeneous and heterogeneous catalysts based on bis(4‐fluorophenyl)methyl‐substituted bis(imino)pyridyliron complexes
Authors: Semikolenova Nina V. , Zhang Wenjuan , Zakharov Vladimir A. , Bryliakov Konstantin P. , Sun Wen‐Hua
Published: July 2015

A series of bis(4‐fluorophenyl)methyl‐substituted bis(imino)pyridyliron chloride complexes were immobilized on oxide supports. The kinetics of ethylene polymerization by both homogeneous and heterogeneous systems was followed, the catalysts mostly demonstrating high activities. The effect of the ligands nature and reaction conditions on the catalytic activities and molecular weights of the resultant polyethylenes was examined. In contrast to homogeneous systems, the supported iron complexes were found to exhibit high and stable activity upon activation with triisobutyl aluminium, producing high‐molecular‐weight polyethylene with good morphology. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42674.
Effect of kaolin nanofiller and processing conditions on the structure, morphology, and biofilm development of polylactic acid
Authors: Segura González Edwin A. , Olmos Dania , González‐Gaitano Gustavo , Orgaz Belén , González‐Benito Javier
Published: July 2015

The effect of high energy ball milling, HEBM, and the presence of kaolin on the structure, morphology, and biofilm development of polylactic acid, PLA, were studied. Biofilm development was evaluated in terms of structural and/or morphological variations so as the sole presence of kaolin. Composites based on PLA filled with kaolin were prepared by HEBM followed by hot pressing to obtain films. Structure was studied by X‐ray diffraction and Fourier transformed infrared spectroscopy whereas morphology was inspected by scanning electron microscopy and atomic force microscopy. To study biofilm development on the surface of these materials, Pseudomonas fluorescens B52 were used. The shear forces from the milling process favor kaolin dispersion within the PLA. Longer milling times and cryogenic conditions improve clay dispersion. Subsequent hot pressing process enhances the most ordered structure of PLA (α‐phase) which is also favored with previous milling at longer times and under cryogenic conditions. Changes in P. fluorescens biofilm development are mainly due to modifications of surface properties induced by structural variations, being the most ordered structures those which better support bacterial adhesion and proliferation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42676.
A dynamic mechanical analysis of the interfacial changes induced from both the reinforcement and the matrix sides in polypropylene/surface modified talc composites
Authors: García‐Martínez Jesús María , Taranco Jesús , Areso Susana , Collar Emilia P.
Published: July 2015

The interfacial changes associated with a series of polypropylene based composite materials with modified interphases from the reinforcement side, from the matrix side and both were studied by following their dynamic mechanical behavior. Composites consisted in an isotactic polypropylene (iPP) matrix, a series of talc with different surface functionalities (hydroxyl, chloride, n‐butyl amine, and silanes) and a commercial interfacial agent form the matrix side (iPP‐SA with 5% of grafts). A comprehensive interpretation of the link existing between the dynamic mechanical responses of the series of 75/25 iPP/talc composites and the molecular relaxation spectrum occurring in the polymer phase of the composites is made with emphasis on the role played by the interfacial modifications performed from each and both sides of the interphase. Dynamic mechanical analysis has been used here to study how the intended interfacial modifications affected the behavior of the composites. The efficiency of the interfacial phenomena is discussed from a phenomenological point of view as well as by considering classical criteria such as the glass transition temperature and the glass to rubbery transition. Finally, a correlation between mechanical parameters from the microscopic scale and others from the macroscopic scale appears to emerge. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42678.
Numerical and experimental studies for gas assisted extrusion forming of molten polypropylene
Authors: Ren Zhong , Huang Xingyuan , Liu Hesheng , Deng Xiaozhen , He Jiantao
Published: July 2015

In this study, the experiments of gas‐assisted extrusion (GAE) for molten polypropylene were carried out under different gas pressures, the different extrudate deformations and sharkskin defects of melt were observed. To ascertain the effects of gas on melt extrusion, non‐isothermal numerical simulation of GAE based on gas/melt two‐phase fluid model was proposed and studied. In the simulations, the melt extruded profile, physical field distributions (velocities, pressure drop, and first normal stress difference) were obtained. Numerical results showed that the deformation degree of melt increased with increasing gas pressure, which was in good agreement with experimental results. It was demonstrated that the influence of gas pressure on the melt extrusion could be well reflected by GAE simulation based on gas/melt two‐phase fluid model rather than simplified‐GAE (SGAE) based on full‐slip wall boundary condition used in the past time. Experimental and numerical results demonstrate that the gas pressure induced first normal stress difference is the main reason of triggering flow behavior changes, extrudate deformations, and sharkskin defects of melt. Therefore, the reasonable controlling of gas pressure is a key in practice of GAE, and the gas layer and its influence should be considered in GAE numerical simulation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42682.
Electrical percolation behavior of carbon fiber and carbon nanotube polymer composite foams: Experimental and computational investigations
Authors: Behbahani Alireza Foroozani , Motlagh Ghodratollah Hashemi , Ziaee Morteza , Nikravan Goolia
Published: July 2015

The effect of foaming on the electrical percolation of polymer composites was simulated by a random sequential additional (RSA) process. Polystyrene composites containing various amounts of carbon fiber (CF) and carbon nanotubes (CNTs) were prepared through melt blending in an internal mixer and subsequently compression‐molded to solid and foam sheets. The electrical conductivity (EC) and percolation threshold (Pc) of both the solid and foam composites were determined to evaluate the simulation results. The experimental results show that the EC of the CF composites decreased with foaming, whereas for the CNT composites, no significant change was observed. The RSA process was used to construct the microstructure of the solid and foam composites and predict their Pcs. Several parameters, including the fiber aspect ratio, bubble volume fraction, and bubble size, were studied by the simulation approach. The Pcs obtained by simulation showed good agreement with the experimental values. When bubbles were excluded to define the volume fraction of the filler, the foam composites with bubbles, close to the fibers in size, had approximately the same Pcs as the solid composites. Better agreement between the experimental and simulation results was found for the foam composites with 30 vol % bubbles rather than those with 15 vol %. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42685.
Silver nanoparticle incorporated poly(l‐lactide‐co‐glycolide) nanofibers: Evaluation of their biocompatibility and antibacterial properties
Authors: Góra Aleksander , Prabhakaran Molamma P. , Eunice Goh Tze Leng , Lakshminarayanan Rajamani , Ramakrishna Seeram
Published: July 2015

The objective of this work is the fabrication of poly(l‐lactide‐co‐glycolide) or PLGA (with LA/GA ratios of 50/50 and 75/25) nanofibers containing silver nanoparticles (AgNPs) by the method of electrospinning. The incorporation of AgNPs in PLGA was carried out in three different concentrations (1, 3, 6 w/w %).The electrospun nanofibers were evaluated for their morphology by scanning electron microscopy and their fiber diameters ranged between 487 and 781 nm. Integration of AgNPs within the fibers was verified by spectroscopy studies, while the mechanical properties of the developed fibers were found comparable to the mechanical properties of the human skin. Proliferation of human dermal fibroblasts (HDF) demonstrated minimal cytotoxicity on fibers containing 1 wt % and 3 wt % of AgNPs, while 6 wt % of AgNPs inhibited cell proliferation. Antimicrobial activity was studied using three different strains of Gram‐positive and Gram‐negative bacteria. Results of the HDF proliferation and antimicrobial studies showed that the electrospun PLGA75/25 containing 3 wt % AgNP can function as a suitable substrate for wound dressing, compared to the other scaffolds of this study. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42686.
Enhanced poly(γ‐glutamic acid) production by H2O2‐induced reactive oxygen species in the fermentation of Bacillus subtilis NX‐2
Authors: Tang Bao , Zhang Dan , Li Sha , Xu Zongqi , Feng Xiaohai , Xu Hong
Published: July 2015

Effects of reactive oxygen species (ROS) on cell growth and poly(γ‐glutamic acid) (γ‐PGA) synthesis were studied by adding hydrogen peroxide to a medium of Bacillus subtilis NX‐2. After optimizing the addition concentration and time of H2O2, a maximum concentration of 33.9 g/L γ‐PGA was obtained by adding 100 µM H2O2 to the medium after 24 H. This concentration was 20.6% higher than that of the control. The addition of diphenyleneiodonium chloride (ROS inhibitor) can interdict the effect of H2O2‐induced ROS. Transcriptional levels of the cofactors and relevant genes were also determined under ROS stress to illustrate the possible metabolic mechanism contributing to the improve γ‐PGA production. The transcriptional levels of genes belonging to the tricarboxylic acid cycle and electron transfer chain system were significantly increased by ROS, which decreased the NADH/NAD+ ratio and increased the ATP levels, thereby providing more reducing power and energy for γ‐PGA biosynthesis. The enhanced γ‐PGA synthetic genes also directly promoted the formation of γ‐PGA. This study was the first to use the ROS control strategy for γ‐PGA fermentation and provided valuable information on the possible mechanism by which ROS regulated γ‐PGA biosynthesis in B. subtilis NX‐2.
Kinetics and Reactor Modeling of the Steam Reforming of Methanol over a Mn‐Promoted Cu/Al Catalyst
Authors: Shi Huancong , Ibrahim Hussameldin , Elamin Mohanned M. , Idem Raphael , Tontiwachwuthikul Paitoon
Published: July 2015

The kinetics of the steam reforming of methanol (SRM) was studied in a packed‐bed reactor over a Mn‐promoted Cu/Al2O3 catalyst under defined conditions. A Langmuir‐Hinshelwood‐Hogan‐Watson (LHHW)‐type mechanism that assumes the dissociative adsorption of methanol on two distinct active sites as the rate‐controlling step was found to satisfactorily describe the SRM reaction with activation energies of 77.3 and 64.5 kJ mol−1 at low and high temperature, respectively. No mass or heat transfer limitations were observed under the experimental conditions used in this study. A reactor model was also developed, validated, and employed to predict the conversion, temperature, and concentration profiles. The axial dispersion had no influence on the temperature distribution but the effect was more pronounced on the methanol conversion.
Roughened Zn‐Doped Ru–Ti Oxide Water Oxidation Electrocatalysts by Blending Active and Activated Passive Components
Authors: Kishor Koshal , Saha Sulay , Gupta Manish Kumar , Bajpai Anshumaan , Chatterjee Moitrayee , Sivakumar Sri , Pala Raj Ganesh S.
Published: July 2015

An approach to decreasing the overpotential, increasing the stability, and optimizing the noble‐metal composition of electrocatalysts for the oxygen evolution reaction (OER) in acidic media is demonstrated. Essential components of this approach are: 1) combining an active (unstable Ru) component with a dopant (Zn)‐activated passive (stable Ti) element, 2) blending these elements by co‐electrodeposition in an acidic environment in which dissolution of the unstable component (excess Ru) promotes roughness, and 3) further increasing the roughness of the resultant electrode through chemical inhomogeneity by the incorporation of Ti and through structural inhomogeneity by incorporation of Zn in RuO2. The composition of the electrode with the maximal activity is Ru0.258Ti0.736Zn0.006Ox, and its activity is four times higher than that of RuO2. The electrochemical stability towards the OER follows the order RuTiZn>RuTi>RuZn>Ru. This design strategy provides a facile method to improve activity without compromising stability.
Development and Validation of an Analytical Model for Predicting Chronoamperometric Responses of Random Arrays of Micro‐ and Nanodisk Electrodes
Authors: Sliusarenko Oleksii , Oleinick Alexander , Svir Irina , Amatore Christian
Published: July 2015

Quantitative theoretical investigations based on a 3D Brownian motion approach established that our previous “cylindrical” approximation remains valid even for drastically irregular arrays. This result led us to propose a simple analytical equation that can be used to predict the chronoamperometric behavior of such commonly used irregular arrays, taking into account the statistical distributions of the Voronoi cells built around the disk electrodes.
Graphenes as Efficient Metal‐Free Fenton Catalysts
Authors: Espinosa Juan C. , Navalón Sergio , Primo Ana , Moral Mónica , Sanz Javier Fernández , Álvaro Mercedes , García Hermenegildo
Published: July 2015

Reduced graphene oxide exhibits high activity as Fenton catalyst with HO. radical generation efficiency over 82 % and turnover numbers of 4540 and 15023 for phenol degradation and H2O2 consumption, respectively. These values compare favorably with those achieved with transition metals, showing the potential of carbocatalysts for the Fenton reaction.
Efficient Self‐Assembly of Di‐, Tri‐, Tetra‐, and Hexavalent Hosts with Predefined Geometries for the Investigation of Multivalency
Authors: Linder Igor , Leisering Stefan , Puttreddy Rakesh , Rades Nadine , Rissanen Kari , Schalley Christoph A.
Published: July 2015

Coordination‐driven self‐assembly of differently shaped di‐ to hexavalent crown‐ether host molecules is described. A series of [21]crown‐7‐ and [24]crown‐8‐substituted bipyridine and terpyridine ligands was synthetized in a “toolbox” approach. Subsequent coordination to 3d transition metal and ruthenium(II) ions provides an easy and fast access to host assemblies with variable valency and pre‐defined orientations of the crown‐ether moieties. Preliminary isothermal calorimetry (ITC) titrations provided promising results, which indicated the host complexes under study to be suitable for the future investigation of multivalent and cooperative binding. The hosts described herein will also be suitable for the construction of various multiply threaded mechanically interlocked molecules.
Morphology‐Tunable Fluorescent Nanoparticles: Synthesis, Photophysical Properties and Two‐Photon Cell Imaging
Authors: Hu Xiaoming , Yin Chao , Hu Wenbo , Yang Zhen , Li Jie , Li Xiang , Lu Xiaomei , Zhao Hui , Tang Yufu , Fan Quli , Huang Wei
Published: July 2015

A novel water‐soluble fluorescent amphiphile based on amino polyethylene glycol (PEG‐NH2) substituted oligo(p‐phenyleneethynylene) (OPE) was designed and synthesized successfully. Taking anion OPE amphiphile as a comparison, the photophysical features were investigated through ultraviolet absorption (UV) and photoluminescence (PL) analyses. Due to the hydrophobic‐hydrophilic property of the OPE conjugated molecule, self‐assembled nanoparticles with the size ranging from 19.6 to 93.5 nm along with the change of morphology from "grain" to "strawberry" were conveniently prepared via adjusting concentrations of OPE aqueous solution. Interestingly, after aging for a period of time, homogeneous hollow nanospheres were spontaneously constructed with a diameter of about 200 nm. Cytotoxicity test and cellular uptake behavior of the nanoparticles were further investigated to evaluate their potential biomedical applications. Subsequently, the promising applications of two‐photon cell imaging were explored using human pancreatic cancer cells (PANC‐1 cells), which indicated that the nanoparticles were mainly located within the cell cytoplasm.
Toward Eco‐friendly Green Organic Semiconductors: Recent Advances in Spiro[fluorene‐9,9′‐xanthene] (SFX)‐Based Optoelectronic Materials and Devices
Authors: Sun Mingli , Xu Ruochen , Xie Linghai , Wei Ying , Huang Wei
Published: July 2015

Green organic semiconductors (GOS) have the four‐element features, including biomass as stuffs, synthesis with the pot, atom and step economic (PASE) route, eco‐friendly fabrication processes in aqueous phase, and recyclable devices, capturing the trend of organic electronics in the future. Herein, we reviewed the efforts that have been made on GOS by our group. We first made a brief introduction of organic (opto)electronics, followed by the design strategies of GOSs based on spirofluorenes. Concretely, we described the discovery of one‐pot protocol to spirofluorenres and a pot‐atom‐step economic (PASE) platform of spiro[fluorene‐9,9′‐xanthene] (SFX) for the molecular design of organic semiconductors, as well as a state‐of‐the‐art nanocrystalline films with eco‐friendly procedures. Then, we highlighted the progress on SFX‐based organic semiconductors in the organic light‐emitting diode (OLED) field. Finally, we conducted a summary on SFXs in OLED and an outlook on green semiconductors starting from biomass, via one‐pot to spirofluorenes, to water‐phase devices.
Photocatalysis using a Wide Range of the Visible Light Spectrum: Hydrogen Evolution from Doped AgGaS2
Authors: Yamato Kohei , Iwase Akihide , Kudo Akihiko
Published: July 2015

Doping of nickel into AgGaS2 yields a new absorption band, at a wavelength longer than the intrinsic absorption band of the AgGaS2 host. The doped nickel forms an electron donor level in a forbidden band of AgGaS2. The nickel‐doped AgGaS2 with rhodium co‐catalyst shows photocatalytic activity for sacrificial H2 evolution under the light of up to 760 nm due to the transition from the electron donor level consisting of Ni2+ to the conduction band of AgGaS2. Apparent quantum yields for the sacrificial H2 evolution at 540–620 nm are about 1 %. Moreover, the nickel‐doped AgGa0.75In0.25S2 also responds to near‐IR light, up to 900 nm.