bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propagation of gravity waves and spread F in the low‐latitude ionosphere over Tucumán, Argentina, by continuous Doppler sounding: First results
Authors: Chum J. , Bonomi F. A. M. , Fišer J. , Cabrera M. A. , Ezquer R. G. , Burešová D. , Laštovička J. , Baše J. , Hruška F. , Molina M. G. , Ise J. E. , Cangemi J. I. , Šindelářová T. 
Published: August 2014

AbstractResults of systematic analysis of propagation directions and horizontal velocities of gravity waves (GWs) and spread F structures in low‐latitude ionosphere (magnetic inclination ~27°) in Tucumán region, Argentina, are presented. Measurements were carried out by multipoint continuous Doppler system during 1 year from December 2012 to November 2013. It was found that meridian propagation of GWs dominated and that southward propagation prevailed in the local summer. Oblique spread structures observed in Doppler shift spectrograms and associated with spread F propagated roughly eastward at velocities from ~70 to ~180 m/s and were observed at night from ~ September to ~ March. The velocities were computed for 182 events and the azimuths for 64 events. Continuous Doppler sounding makes it possible to analyze more events compared to optical observations often used for propagation studies since the measurements do not depend on weather.
Investigation of a mesospheric gravity wave ducting event using coordinated sodium lidar and Mesospheric Temperature Mapper measurements at ALOMAR, Norway (69°N)
Authors: Bossert Katrina , Fritts David C. , Pautet Pierre‐Dominique , Taylor Michael J. , Williams Bifford P. , Pendelton William R. 
Published: August 2014

AbstractNew measurements at the ALOMAR observatory in northern Norway (69°N, 16°E) using the Weber sodium lidar and the Advanced Mesospheric Temperature Mapper (AMTM) allow for a comprehensive investigation of a gravity wave (GW) event on 22 and 23 January 2012 and the complex and varying propagation environment in which the GW was observed. These observational techniques provide insight into the altitude ranges over which a GW may be evanescent or propagating and enable a clear distinction in specific cases. Weber sodium lidar measurements provide estimates of background temperature, wind, and stability profiles at altitudes from ~78 to 105 km. Detailed AMTM temperature maps of GWs in the OH emission layer together with lidar measurements quantify estimates of the observed and intrinsic GW parameters centered near 87 km. Lidar measurements of sodium densities also allow more precise identification of GW phase structures extending over a broad altitude range. We find for this particular event that the extent of evanescent regions versus regions allowing GW propagation can vary largely over a period of hours and significantly change the range of altitudes over which a GW can propagate.
The influence of canopy snow parameterizations on snow albedo feedback in boreal forest regions
Authors: Thackeray Chad W. , Fletcher Christopher G. , Derksen Chris 
Published: August 2014

AbstractVariation in snow albedo feedback (SAF) among Coupled Model Intercomparison Project phase 5 climate models has been shown to explain much of the variation in projected 21st century warming over Northern Hemisphere land. Prior studies using observations and models have demonstrated both considerable spread in the albedo and a negative bias in the simulated strength of SAF, over snow‐covered boreal forests. Boreal evergreen needleleaf forests are capable of intercepting snowfall throughout the winter and consequently exert a significant impact on seasonal surface albedo. Two satellite data products and tower‐based observations of albedo are compared with simulations from multiple versions of the Community Climate System Model (CCSM4) to investigate the causes of weak simulated SAF over the boreal forest. The largest bias occurs in April and May, when simulated SAF is one half the strength of SAF in observations. This is traced to two features of the canopy snow parameterizations used in the land model. First, there is no mechanism for the dynamic removal of snow from the canopy when temperatures are below freezing, which results in albedo values in midwinter that are biased high. Second, when temperatures do rise above freezing, all snow on the canopy is melted instantaneously, which results in an unrealistically early transition from a snow‐covered to a snow‐free canopy. These processes combine to produce large differences between simulated and observed monthly albedo and are the source of the weak bias in SAF. This analysis highlights the importance of canopy snow parameterizations for simulating the hemispheric scale climate response to surface albedo perturbations.
Middle Miocene climate instability associated with high‐amplitude CO2 variability
Authors: Greenop Rosanna , Foster Gavin L. , Wilson Paul A. , Lear Caroline H. 
Published: August 2014

AbstractThe amplitude of climatic change, as recorded in the benthic oxygen isotope record, has varied throughout geological time. During the late Pleistocene, changes in the atmospheric concentration of carbon dioxide (CO2) are an important control on this amplitude of variability. The contribution of CO2 to climate variability during the pre‐Quaternary however is unknown. Here we present a new boron isotope‐based CO2 record for the transition into the middle Miocene Climatic Optimum (MCO) between 15.5 and 17 Myr that shows pronounced variability between 300 ppm and 500 ppm on a roughly 100 kyr time scale during the MCO. The CO2 changes reconstructed for the Miocene are ~2 times larger in absolute terms (300 to 500 ppm compared to 180 to 280 ppm) than those associated with the late Pleistocene and ~15% larger in terms of climate forcing. In contrast, however, variability in the contemporaneous benthic oxygen isotope record (at ~1‰) is approximately two thirds the amplitude of that seen during the late Pleistocene. These observations indicate a lower overall sensitivity to CO2 forcing for Miocene (Antarctic only) ice sheets than their late Pleistocene (Antarctic plus lower latitude northern hemisphere) counterparts. When our Miocene CO2 record is compared to the estimated changes in contemporaneous δ18Osw (ice volume), they point to the existence of two reservoirs of ice on Antarctica. One of these reservoirs appears stable, while a second reservoir shows a level of dynamism that contradicts the results of coupled climate‐ice sheet model experiments given the CO2 concentrations that we reconstruct.
A Quick and Easy Strategy to Reduce Test Anxiety and Enhance Test Performance
Authors: Mavilidi Myrto‐Foteini , Hoogerheide Vincent , Paas Fred 
Published: August 2014

SummaryThe negative thoughts that anxious children experience while sitting for an exam consume working memory resources at the cost of resources for performing on the exam. In a randomized field experiment (N = 117) with primary school students, we investigated the hypothesis that stimulating students to look through the problems of a math test before they start solving them would reduce anxiety, release these anxiety‐related working memory resources, and lead to higher test performance than not allowing students to look ahead in the test. The results confirmed the hypothesis, indicating that the positive effects of looking ahead applied to all students, regardless of their anxiety level (low, medium, or high). The results suggest that by looking ahead in a test, less working memory resources are consumed by intrusive thoughts, and consequently, more resources can be used for performing on the test. Theoretical and practical implications of the results are discussed. Copyright © 2014 John Wiley & Sons, Ltd.
Synthese Stickstoff‐dotierter Zickzackkanten: Dibenzo‐9a‐azaphenalen als molekularer Baustein
Authors: Berger Reinhard , Giannakopoulos Angelos , Ravat Prince , Wagner Manfred , Beljonne David , Feng Xinliang , Müllen Klaus 
Published: August 2014

AbstractEine Bottom‐up‐Methode zur Synthese stabiler und monodisperser Graphensegmente mit Stickstoff‐dotierten Zickzackkanten wird vorgestellt. Auf Grundlage des bisher unbeschriebenen Dibenzo‐9a‐azaphenalens (DBAPhen) als molekularer Baustein wird ein allgemein anwendbares Konzept zur Synthese ausgedehnter Nanographene und Nanographenstreifen mit Stickstoff‐dotierten Zickzackkanten eingeführt.
Characterizing Methyl‐Bearing Side Chain Contacts and Dynamics Mediating Amyloid β Protofibril Interactions Using 13Cmethyl‐DEST and Lifetime Line Broadening
Authors: Fawzi Nicolas L. , Libich David S. , Ying Jinfa , Tugarinov Vitali , Clore G. Marius 
Published: August 2014

AbstractMany details pertaining to the formation and interactions of protein aggregates associated with neurodegenerative diseases are invisible to conventional biophysical techniques. We recently introduced 15N dark‐state exchange saturation transfer (DEST) and 15N lifetime line‐broadening to study solution backbone dynamics and position‐specific binding probabilities for amyloid β (Aβ) monomers in exchange with large (2–80 MDa) protofibrillar Aβ aggregates. Here we use 13Cmethyl DEST and lifetime line‐broadening to probe the interactions and dynamics of methyl‐bearing side chains in the Aβ‐protofibril‐bound state. We show that all methyl groups of Aβ40 populate direct‐contact bound states with a very fast effective transverse relaxation rate, indicative of side‐chain‐mediated direct binding to the protofibril surface. The data are consistent with position‐specific enhancements of 13Cmethyl‐${R{{{\rm tethered}\hfill \atop 2\hfill}}}$ values in tethered states, providing further insights into the structural ensemble of the protofibril‐bound state.
Magnetic‐Structure‐Stabilized Polarization in an Above‐Room‐Temperature Ferrimagnet
Authors: Li Man‐Rong , Retuerto Maria , Walker David , Sarkar Tapati , Stephens Peter W. , Mukherjee Swarnakamal , Dasgupta Tanusri Saha , Hodges Jason P. , Croft Mark , Grams Christoph P. , Hemberger Joachim , Sánchez‐Benítez Javier , Huq Ashfia , Saouma Felix O. , Jang Joon I. , Greenblatt Martha 
Published: August 2014

AbstractAbove‐room‐temperature polar magnets are of interest due to their practical applications in spintronics. Here we present a strategy to design high‐temperature polar magnetic oxides in the corundum‐derived A2BB′O6family, exemplified by the non‐centrosymmetric (R3) Ni3TeO6‐type Mn2+2Fe3+Mo5+O6, which shows strong ferrimagnetic ordering withTC=337 K and demonstrates structural polarization without any ions with (n−1)d10ns0, d0, or stereoactive lone‐pair electrons. Density functional theory calculations confirm the experimental results and suggest that the energy of the magnetically ordered structure, based on the Ni3TeO6prototype, is significantly lower than that of any related structure, and accounts for the spontaneous polarization (68 μC cm−2) and non‐centrosymmetry confirmed directly by second harmonic generation. These results motivate new directions in the search for practical magnetoelectric/multiferroic materials.
N‐Heterocyclic Carbene Catalyzed Formal [3+2] Annulation Reaction of Enals: An Efficient Enantioselective Access to Spiro‐Heterocycles
Authors: Guo Chang , Schedler Michael , Daniliuc Constantin G. , Glorius Frank 
Published: August 2014

AbstractA highly enantioselective N‐heterocyclic carbene (NHC) catalyzed formal [3+2] annulation of α,β‐unsaturated aldehydes with azaaurones or aurone generating spiro‐heterocycles has been developed. The protocol represents a unique NHC‐activation‐based approach to access spiro‐heterocyclic derivatives bearing a quaternary stereogenic center with high optical purity (up to 95 % ee).
Phosphorous antioxidants against polypropylene thermal degradation during rotational molding‐kinetic modeling
Authors: Sarrabi Salah , Lacrampe Marie‐France , Krawczak Patricia 
Published: August 2014

ABSTRACTPhosphorous antioxidants efficiency against molten polypropylene (PP) thermal oxidation was assessed during isothermal ageing and processing by rotational molding. During isothermal ageing, experimental data were compared to the ones calculated on the basis of a kinetic model. Phosphonite is more effective than phosphite. Both phosphite and phosphonite decompose hydroperoxide and prevent initiation of oxidation reactions. However, phosphonite hydrolysis product acts as a radical chain terminator and blocks propagation reactions. Kinetic constants of stabilization reactions were evaluated and discussed. Further, this kinetic modeling was coupled to a thermal software, able to predict polymer temperature evolution during rotational molding and the degradation critical temperature (DCT) of different stabilized PP. A DCT of 235°C was obtained for PP stabilized with phosphonite and hindered phenol against 215°C for PP stabilized with phosphite and the same phenol. This difference of 20°C, corresponding to 5 min more heating is significant to optimize rotational molding. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41285.
Iron‐catalyzed depolymerization of polysiloxanes to produce dichlorodimethylsilane, diacetoxydimethylsilane, or dimethoxydimethylsilane
Authors: Enthaler Stephan 
Published: August 2014

ABSTRACTPolymers are one of the important pillars of our current society. Besides the great success a matter is the accumulation of huge amounts of end‐of‐life polymers. Current waste management bases primarily on landfills, thermal recycling, and down‐cycling. Noteworthy, only a small part of the end‐of‐life materials is recycled by depolymerization, means low‐molecular weight synthons are created, which can be polymerized to new polymers to close the cycle. Widely used polymers in modern life times are silicones (polysiloxanes). Based on the intrinsic properties the depolymerization is challenging and only a few high temperature or less environmental‐friendly processes have been reported. In this regard, we have set up a capable low‐temperature protocol for the depolymerization of silicones with acid chlorides, acetic acid, or methanol in the presence of cheap iron salts as precatalysts to yield dichlorodimethylsilane, diacetoxydimethylsilane, or dimethoxydimethylsilane as well‐defined products. Notably, dichlorodimethylsilane, diacetoxydimethylsilane, and dimethoxydimethylsilane can be useful starting materials for synthesizing new polymers; overall a recycling is feasible. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41287.
Dielectric and gas transport properties of the films of thermally stable poly(arylene ether ketone)s containing content‐tunable benzimidazole moiety
Authors: Liao Junbin , Chu Youqun , Wang Jianli , Zhou Meiqing , Cao Yiming 
Published: August 2014

ABSTRACTA series of thermally stable poly(arylene ether ketone)s (PAEKs) bearing benzimidazole structure in the main chains, named poly(arylene ether ketone‐benzimidazole)s (PAEK‐BIs), were directly synthesized by polycondensation of dimethyl bisphenol, dibenzimidazole bisphenol, and difluorobenzophenones. By systematically varying the amount ratio of two kind of bisphenols, the content of benzimidazole moiety in the backbone was controlled straightforwardly. The prepared amorphous polymers were characterized in terms of Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, thermal, dielectric, and gas transport properties. Evaluation of solubility reveals that PAEK‐BIs with >60% content of benzimidazole units could be soluble in commonly used organic solvents. Also polymers containing content‐tunable benzimidazole show high glass‐transition temperatures (Tg's, 157–319°C) and excellent thermal stability (e.g., temperature of 5% weight loss, above 438°C in air). Dielectric constants of PAEK‐BIs measured at 25°C are all less than 2.66 in the frequency range of 0.1–50 kHz. For dense films, the ideal gas selectivity and permeability coefficients could be compared with that of commercial Ultem 1000 membrane, which indicate that the PAEK‐BIs are potential to be used for gas separation membrane material. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41289.
Sorption and thermal properties of strongly basic cross‐linked ionic polymer modified with Cr(III) compounds
Authors: Gutsanu Vasile , Lisa Gabriela , Vizir Constantin , Tudorachi Nita 
Published: August 2014

ABSTRACTAV‐17(Cr) material was prepared by modifying a commercial polymer AV‐17 (initially bearing R4N+ functional groups) with Cr(III) compounds was investigated. Comparative isotherms characterizing the
and
ion sorption from solution with pH values of 3 and 8, respectively, at 19°C and 60°C, were obtained using the raw AV‐17(Cl) and the modified AV‐17(Cr) material. The sorption process on AV‐17(Cr) takes place through the coordination of Cr(VI) ions with Cr(III) ions, while on AV‐17(Cl) it is due to an ion exchange mechanism. The sorption isotherms obtained in pH 8 solutions fit perfectly the Langmuir model. The thermodynamic functions ΔG, ΔH, and ΔS characteristic to the adsorption of
ions from K2CrO4 solutions with pH = 8 were calculated. The active sites belonging to the AV‐17(Cr) material were identified as jarosite type compounds of Cr(III). SEM images show that the Cr(III) compounds are present in the form of ultrafine particles located on the surface and within the bulk phase of the polymer granules. Comparative thermal degradation process of both the AV‐17(Cr) and the AV‐17(Cl) material was conducted in air and in an inert atmosphere (He). The thermal degradation mechanism of sorbent AV‐17(Cr) and exchanger AV‐17(Cl) is proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41306.
Tissue alterations in urethral and vaginal walls related to multiparity in rabbits
Authors: Xelhuantzi Nicte , Rodríguez‐Antolín Jorge , Nicolás Leticia , Castelán Francisco , Cuevas Estela , Martínez‐Gómez Margarita 
Published: August 2014

ABSTRACTIn rodents, vaginal distention after delivery or experimental manipulation affects innervations as well as the amount of striated/smooth musculature or collagen in both the urethra and vagina. These changes are associated with modifications in excretory and reproductive processes. Although successive and consecutive vaginal deliveries (multiparity) affect the contractile and functional properties of the female lower urogenital tract (LUT), its impact on LUT morphometry, including persistency, has been barely studied. The caudal urethra (CU) and cranial (V1) and caudal (V2) pelvic vaginal regions were excised from young and adult nulliparous (YN and AN, respectively) and multiparous (YM and AM, respectively) rabbits. Tissues were histologically processed and stained with Masson's trichrome. The thickness of the tissue layers and areas covered by tissue components were measured and compared using two‐way ANOVA followed by Student‐Newmann‐Keuls tests to determine statistical differences (P ≤ 0.05). Compared to YN, YM, and AN tissues showed a reduction in the thickness of the epithelium, as well as in areas covered by striated musculature, collagen, and blood vessels of the LUT. In comparison with YM, only some morphometric changes were recovered in the AM group. Our study shows that multiparity and age can be associated with epithelial and muscular atrophy of urethral and vaginal walls. The morphometry of the LUT between young and adult female rabbits varies with multiparity. These findings may help to better understand the effects of multiparity on young and adult females and its correlation with the development of pelvic dysfunctions. Anat Rec, 297:1963–1970, 2014. © 2014 Wiley Periodicals, Inc.
Thirty‐Day Hospital Readmissions in Systemic Lupus Erythematosus: Predictors and Hospital‐ and State‐Level Variation
Authors: Yazdany Jinoos , Marafino Ben J. , Dean Mitzi L. , Bardach Naomi S. , Duseja Reena , Ward Michael M. , Dudley R. Adams 
Published: August 2014

ObjectiveSystemic lupus erythematosus (SLE) has one of the highest hospital readmission rates among chronic conditions. This study was undertaken to identify patient‐level, hospital‐level, and geographic predictors of 30‐day hospital readmissions associated with SLE.MethodsUsing hospital discharge databases from 5 geographically dispersed states, we studied all‐cause readmission of SLE patients between 2008 and 2009. We evaluated each hospitalization as a possible index event leading up to a readmission, our primary outcome. We accounted for clustering of hospitalizations within patients and within hospitals and adjusted for hospital case mix. Using multilevel mixed‐effects logistic regression, we examined factors associated with 30‐day readmission and calculated risk‐standardized hospital‐level and state‐level readmission rates.ResultsWe examined 55,936 hospitalizations among 31,903 patients with SLE. Of these hospitalizations, 9,244 (16.5%) resulted in readmission within 30 days. In adjusted analyses, age was inversely related to risk of readmission. African American and Hispanic patients were more likely to be readmitted than white patients, as were those with Medicare or Medicaid insurance (versus private insurance). Several clinical characteristics of lupus, including nephritis, serositis, and thrombocytopenia, were associated with readmission. Readmission rates varied significantly between hospitals after accounting for patient‐level clustering and hospital case mix. We also found geographic variation, with risk‐adjusted readmission rates lower in New York and higher in Florida as compared to California.ConclusionWe found that ∼1 in 6 hospitalized patients with SLE were readmitted within 30 days of discharge, with higher rates among historically underserved populations. Significant geographic and hospital‐level variation in risk‐adjusted readmission rates suggests potential for quality improvement.
Metallogel Template Fabrication of pH‐Responsive Copolymer Nanowires Loaded with Silver Nanoparticles and Their Photocatalytic Degradation of Methylene Blue
Authors: Wen Xing , Tang Liming , Li Botian 
Published: August 2014

AbstractPoly(N,N′‐methylenebisacrylamide–4‐vinylpyridine) (P(MBA‐4VP)) nanowires loaded with silver nanoparticles (Ag NPs) have been fabricated by silver metallogel template copolymerization, and subsequently, silver ions are reduced instead of the template being removed. Ag NPs with a diameter of 5–15 nm were dispersed throughout the core of P(MBA‐4VP) nanowires. The size and distribution of the formed Ag NPs could be finely controlled by reduction time. The pH sensitivity of P(MBA‐4VP) nanowires offers the possibility of Ag NP release from the nanowires under acidic conditions. The photocatalytic performance of the P(MBA‐4VP) nanowires loaded with Ag NPs was evaluated for the degradation of methylene blue (MB) under UV light irradiation. Their rate of degradation is dependent on the content and size of the Ag NPs, as well as the pH values of the MB solution. Moreover, the P(MBA‐4VP) nanowires loaded with Ag NPs exhibited high photostability, and the photocatalytic efficiency reduced by only 1.81 % after being used three times.
Self‐Assembly of Pyridinium‐Tailored Anthracene Amphiphiles into Supramolecular Hydrogels
Authors: Wang Peiyi , Hu Jun , Yang Song , Song Baoan , Wang Qian 
Published: August 2014

AbstractThe mixing of a polyacid cross‐linker with a pyridinium‐functionalized anthracene amphiphile afforded a supramolecular hydrogel through a self‐assembly process that was primarily driven by π‐stacking and electrostatic interactions.