bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation Mechanism of NF4+ Salts and Extraordinary Enhancement of the Oxidizing Power of Fluorine by Strong Lewis Acids
Authors: Christe Karl O. , Haiges Ralf , Vasiliu Monica , Dixon David A. 
Published: May 2017

AbstractAlthough the existence of the NF4+ cation has been known for 51 years, and its formation mechanism from NF3 , F2 , and a strong Lewis acid in the presence of an activation energy source had been studied extensively, the mechanism had not been established. Experimental evidence had shown that the first step involves the generation of F atoms from F2 , and also that the NF3+ cation is a key intermediate. However, it was not possible to establish whether the second step involved the reaction of a F atom with either NF3 or the Lewis acid (LA). To distinguish between these two alternatives, a computational study of the NF4 , SbF6 , AsF6 , and BF4 radicals was carried out. Whereas the heats of reaction are small and similar for the NF4 and LAF radicals, at the reaction temperatures, only the LAF radicals possess sufficient thermal stability to be viable species. Most importantly, the ability of the LAF radicals to oxidize NF3 to NF3+ demonstrates that they are extraordinary oxidizers. This extraordinary enhancement of the oxidizing power of fluorine with strong Lewis acids had previously not been fully recognized.
Ultraschnelle Schichtablösung von Graphit zu qualitativ hochwertigem Graphen durch Nutzung von Wechselstrom
Authors: Yang Sheng , Ricciardulli Antonio Gaetano , Liu Shaohua , Dong Renhao , Lohe Martin R. , Becker Alfons , Squillaci Marco A. , Samorì Paolo , Müllen Klaus , Feng Xinliang 
Published: May 2017

AbstractUm die Lücke zwischen Forschung im Labormaßstab und kommerzieller Anwendung zu schließen, ist die Massenproduktion von qualitativ hochwertigem Graphen unerlässlich. Hier wird eine skalierbare Exfolierungsstrategie beschrieben, die zur Herstellung von Graphenplättchen mit hohem Ertrag (75 %, 1–3 Schichten), geringer Defektdichte (C/O‐Verhältnis von 21.2), sehr guter Verarbeitbarkeit in Lösung und hervorragenden elektronischen Eigenschaften (Loch‐Mobilität von 430 cm2 V−1 s−1) führt. Durch die Anwendung von Wechselstrom erfolgt eine gleichzeitige Exfolierung an beiden Graphitelektroden, welche eine hohe Produktionsrate von über 20 g h−1 im Labormaßstab ermöglicht. Als Kathodenmaterial für Lithiumspeicher verfügen mit Graphen ummantelte LiFePO4‐Partikel über eine hohe Kapazität von 167 mAh g−1 bei einer C‐Rate von 1 nach 500 Zyklen.
Betaine Catalysis for Hierarchical Reduction of CO2 with Amines and Hydrosilane To Form Formamides, Aminals, and Methylamines
Authors: Liu Xiao‐Fang , Li Xiao‐Ya , Qiao Chang , Fu Hong‐Chen , He Liang‐Nian 
Published: May 2017

AbstractAn efficient, sustainable organocatalyst, glycine betaine, was developed for the reductive functionalization of CO2 with amines and diphenylsilane. Methylamines and formamides were obtained in high yield by tuning the CO2 pressure and reaction temperature. Based on identification of the key intermediate, that is, the aminal, an alternative mechanism for methylation involving the C0 silyl acetal and aminal is proposed. Furthermore, reducing the CO2 amount afforded aminals with high yield and selectivity. Therefore, betaine catalysis affords products with a diversified energy content that is, formamides, aminals and methylamines, by hierarchical two‐, four‐ and six‐electron reduction, respectively, of CO2 coupled with C−N bond formation.
Chain Multiplication of Fatty Acids to Precise Telechelic Polyethylene
Authors: Witt Timo , Häußler Manuel , Kulpa Stefanie , Mecking Stefan 
Published: May 2017

AbstractStarting from common monounsaturated fatty acids, a strategy is revealed that provides ultra‐long aliphatic α,ω‐difunctional building blocks by a sequence of two scalable catalytic steps that virtually double the chain length of the starting materials. The central double bond of the α,ω‐dicarboxylic fatty acid self‐metathesis products is shifted selectively to the statistically much‐disfavored α,β‐position in a catalytic dynamic isomerizing crystallization approach. “Chain doubling” by a subsequent catalytic olefin metathesis step, which overcomes the low reactivity of this substrates by using waste internal olefins as recyclable co‐reagents, yields ultra‐long‐chain α,ω‐difunctional building blocks of a precise chain length, as demonstrated up to a C48 chain. The unique nature of these structures is reflected by unrivaled melting points (Tm=120 °C) of aliphatic polyesters generated from these telechelic monomers, and by their self‐assembly to polyethylene‐like single crystals.
A Twisted Nanographene Consisting of 96 Carbon Atoms
Authors: Cheung Kwan Yin , Chan Chi Kit , Liu Zhifeng , Miao Qian 
Published: May 2017

AbstractHerein we report synthesis, structure and properties of a new type of twisted nanographene, which contains an [8]circulene moiety in a polycyclic framework of 96 sp2 carbon atoms. The key steps in this synthesis are the Diels–Alder reaction of a macrocyclic diyne and the subsequent Scholl reaction forming the [8]circulene moiety. Two incompletely cyclized products were isolated from the Scholl reaction, providing insight into the cyclization of the strained octagon. This nanographene is twisted along two directions with end‐to‐end twists of 142.4° and 140.2° as revealed by X‐ray crystallography, and is flexible at room temperature as found from the computational and experimental studies.
Lithiophilic Sites in Doped Graphene Guide Uniform Lithium Nucleation for Dendrite‐Free Lithium Metal Anodes
Authors: Zhang Rui , Chen Xiao‐Ru , Chen Xiang , Cheng Xin‐Bing , Zhang Xue‐Qiang , Yan Chong , Zhang Qiang 
Published: May 2017

AbstractLithium (Li) metal is the most promising electrode for next‐generation rechargeable batteries. However, the challenges induced by Li dendrites on a working Li metal anode hinder the practical applications of Li metal batteries. Herein, nitrogen (N) doped graphene was adopted as the Li plating matrix to regulate Li metal nucleation and suppress dendrite growth. The N‐containing functional groups, such as pyridinic and pyrrolic nitrogen in the N‐doped graphene, are lithiophilic, which guide the metallic Li nucleation causing the metal to distribute uniformly on the anode surface. As a result, the N‐doped graphene modified Li metal anode exhibits a dendrite‐free morphology during repeated Li plating and demonstrates a high Coulombic efficiency of 98 % for near 200 cycles.
Photopolymer resins for luminescent three‐dimensional printing
Authors: Wang Fei , Chong Yiting , Wang FuKe , He Chaobin 
Published: May 2017

ABSTRACTLiquid resins‐based three‐dimensional (3D) printing techniques such as stereolithography and digital light processing (DLP) show higher resolution and accuracy than other printing techniques, but their applications have been impeded by the limited materials selection and lack of functions. We here reported the preparation of luminescent resins for DLP‐based 3D printing. Homogeneous dispersion of the fluorescent dyes was achieved by small acrylate molecules screening, and the cure depth studies was used to optimize both resin composition and printing parameters setting. In addition, we showed that the optical analysis of absorption and emission spectra is an important tool to reduce the complex mutual‐interference of the light absorption of dye, photoinitiator and photo‐absorber in the printable resin. We also developed the mater batch technique to tune the emitting colors in the whole visible range, together with white emitting. By using the developed resins, different 3D structures with different emitting colors were successfully printed by DLP technique. These results will further widen the applications of the liquid resins‐based 3D printing techniques, and these luminescent resins show highly potential applications in education, lighting, UV converters, and so on. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44988.
Sky detection‐ and texture smoothing‐based high‐visibility haze removal from images and videos
Authors: Liu Chunxiao , Shen Yiyun , Shao Yaqi , Zhao Jinwei , Wang Xun 
Published: May 2017

AbstractTo address the gloomy sky and the low contrast caused by the left fog in the existing image dehazing methods, we propose a robust haze removal algorithm for images and videos. First, a sky detection‐based adaptive atmospheric light estimation method is designed for brighter and cleaner restoration results for the sky regions. Second, in order to reconstruct a transmission map in line with the depth variation, we preprocess the input image with texture smoothing to keep the color consistency inside the same planar object and devise a texture smoothing‐based robust transmission estimation method, with which the contrast and color saturation of fog‐free image are greatly promoted. Finally, the restored results are post‐processed with the joint bilateral filter for the purpose of noise removal. What's more, a guided filter‐based temporally coherent atmospheric light smoothing strategy and a Gaussian filter‐based spatial‐temporally coherent transmission smoothing strategy are put forward for video dehazing, which can ensure the spatial as well as temporal continuity of the haze‐free videos. Experimental results show that the recovered haze‐free images and videos have high contrast and color saturation with cleaner sky regions, and the haze‐free videos are free of jittering and flickering phenomena.
Designing quality into direct‐assessment competency‐based education
Authors: Brower Aaron M. , Humphreys Debra , Karoff Rebecca , Kallio Sandra 
Published: May 2017

BackgroundMeeting the nation's need for 60% of its working age population to hold postsecondary education by 2025 is not possible through traditional educational institutions and formats. They simply do not have the “seats” available. Students, employers, and regulatory agencies are actively exploring educational alternatives, such as competency‐based education, rightfully expecting assurances of quality.MethodsIn this study, we apply design principles using the Association of American Colleges & Universities quality framework to direct‐assessment CBE. This quality framework arises from AAC&U's Liberal Education and America's Promise. The University of Wisconsin Flexible Option (UW Flex) is used to illustrate the application of the AAC&U quality framework.FindingsThe LEAP design principles are used to create an aspirational vision to guide the development of direct‐assessment CBE. We describe the work and design decisions made when creating UW Flex to illustrate how the LEAP quality framework can ensure high‐quality direct‐assessment CBE programming.ConclusionThis study builds the case for how quality CBE can expand opportunities for more Americans. We promote a particular vision of quality that is an aspirational model for CBE, based on the AAC&U LEAP design principles of Proficiency, Agency and Self‐Direction, Integrative Learning and Problem‐Based Inquiry, Transparency and Assessment, and Equity. The intense excitement over CBE presents an unprecedented opportunity to design high‐quality educational models that focus emphatically on student learning versus faculty teaching, allowing higher education leaders to remove impediments to optimal learning. Only then will all students have the chance to reach the levels of talent and ability needed to navigate and flourish in today's world.
FeII/FeIII Doped Bi/BiOBr Hierarchical Microspheres as a Highly Efficient Catalyst for Degradation of Organic Contaminants at Neutral pH: The Role of Visible Light and H2O2
Authors: Li Wentao , Geng Xin , Xiao Feng , An Guangyu , Wang Dongsheng 
Published: May 2017

AbstractA novel FeII/FeIII doped Bi/BiOBr (FBB) visible‐light, Fenton‐like catalyst was successfully synthesized by using the solvothermal method. The morphological and structural features of FBB were analyzed by XRD, field emission (FE)‐SEM, TEM, Brunauer–Emmett–Teller (BET), and X‐ray photoelectron spectroscopy (XPS) techniques. The results revealed that the presence of Fe could promote the growth of Bi metal nanoparticles, and increase the specific surface areas of FBB. Rhodamine B (RhB) photodegradation experiments indicated that FBB with the Fe/Bi molar ratio (0.2–0.3) exhibited higher photocatalytic activities. In the photo‐Fenton‐like reaction, the degradation efficiency of bisphenol A (BPA) over FBB‐25 was increased to 100 % within 30 min whereas it was 3 % and 12 % in the Fenton‐like and photocatalytic reactions. Moreover, 2‐chlorophenol (2‐CP), 4‐chlorophenol (4‐CP), 2,4‐dichlorophenol (2,4‐DCP), and 2,4,6‐trichlorophenol (2,4,6‐TCP) were completely degraded within 30 min over FBB‐25. The presence of visible light can promote the rapid reaction rate between FeII and FeIII over FBB with H2O2, producing more hydroxyl radicals (.OH) and more holes. The radical scavenger experiments demonstrated that holes and hydroxyl radicals (.OH) were the main active species. FBB‐25 is still stable after five cycles. Therefore, FBB‐25 has great potential in wastewater treatment.
Polymorph Control of L‐ArgHCl on Antisolvent Crystallization by Ultrasonic Irradiation
Authors: Ike Yuki , Hirasawa Izumi 
Published: May 2017

AbstractAmino acids are utilized as medical raw materials and food additives. It is well‐known that most of the amino acids show polymorphism. Differences in the crystal structures affect the physical and chemical properties. Therefore, an effective method for polymorph control is required in the crystallization process. Polymorph control of L‐arginine hydrochloride (L‐ArgHCl) on antisolvent crystallization was achieved by ultrasonic irradiation. L‐ArgHCl exhibits polymorphism and crystallizes into three distinct crystal forms. Without irradiation, the metastable form was selectively crystallized. In contrast, the unstable form was selectively crystallized by irradiation. Irradiation after the addition of an antisolvent led to a shorter induction time.
N‐BODIPYs Come into Play: Smart Dyes for Photonic Materials
Authors: Ray César , Díaz‐Casado Laura , Avellanal‐Zaballa Edurne , Bañuelos Jorge , Cerdán Luis , García‐Moreno Inmaculada , Moreno Florencio , Maroto Beatriz L. , López‐Arbeloa Íñigo , de la Moya Santiago 
Published: May 2017

AbstractN‐BODIPYs (diaminoboron dipyrromethenes) are unveiled as a new family of BODIPY dyes with huge technological potential. Synthetic access to these systems has been gained through a judicious design focused on stabilizing the involved diaminoboron chelate. Once stabilized, the obtained N‐BODIPYs retain the effective photophysical behavior exhibited by other boron‐substituted BODIPYs, such as O‐BODIPYs. However, key bonding features of nitrogen compared to those of oxygen (enhanced bond valence and different bond directionality) open up new possibilities for functionalizing BODIPYs, allowing an increase in the number of pendant moieties (from two in O‐BODIPYs, up to four in N‐BODIPYs) near the chromophore and, therefore, greater control of the photophysics. As a proof of concept, the following findings are discussed: (1) the low‐cost and straightforward synthesis of a selected series of N‐BODIPYs; (2) their outstanding photophysical properties compared to those of related effective dyes (excellent emission signatures, including fluorescence in the solid state; notable lasing capacities in the liquid phase and when doped into polymers; improved laser performance compared to the parent F‐BODIPYs); (3) the versatility of the diaminoboron moiety in allowing the generation of multifunctionalized BODIPYs, permitting access to both symmetric and asymmetric dyes; (4) the capability of such versatility to finely modulate the dye photophysics towards different photonic applications, from lasing to chemosensing.
Glucose‐Modified Silicon Nanoparticles for Cellular Imaging
Authors: Hsu Chien‐Wei , Septiadi Dedy , Lai Chian‐Hui , Chen Pengkun , Seeberger Peter H. , De Cola Luisa 
Published: May 2017

AbstractLuminescent silicon nanoparticles have recently attracted attention due to their remarkable stability, covalent functionalisation and tunable photoemission properties. Owing to their biocompatibility, low toxicity, and the small particle size that can be achieved by different synthetic approaches, these nanomaterials are candidates as cellular probes in the field of bioimaging, and potentially for in vivo applications. Tailoring the surface of the particles with active biomolecules such as sugar moieties can be an interesting strategy to increase the kinetics of internalisation or to vary the localisation of nanosystems in living cells. In this study, we synthesised and modified ultrasmall silicon nanoparticles with glucose covalently linked on their surface. Moreover, by varying the ratio between the amount of silicon nanoparticles and the saccharide groups, the amount of glucose, as a capping moiety, can be well controlled. FTIR spectroscopy, NMR spectroscopy, zeta potential measurements and anisotropy decay analysis confirmed the covalent binding of glucose to the nanoparticles. The photophysical behaviour of the surface‐functionalised silicon quantum dots was not significantly different to that of the unmodified nanoparticles. In vitro studies demonstrated faster internalisation of the glucose‐functionalised nanoparticles into HeLa cells. Different localisation and uptake kinetics of the glucose‐modified particles compared to the unmodified particles are discussed in order to reveal the role played by the sugar molecules.
Polybenzoxazine‐Derived N‐doped Carbon as Matrix for Powder‐Based Electrocatalysts
Authors: Barwe Stefan , Andronescu Corina , Masa Justus , Ventosa Edgar , Klink Stefan , Genç Aziz , Arbiol Jordi , Schuhmann Wolfgang 
Published: May 2017

AbstractIn addition to catalytic activity, intrinsic stability, tight immobilization on a suitable electrode surface, and sufficient electronic conductivity are fundamental prerequisites for the long‐term operation of particle‐ and especially powder‐based electrocatalysts. We present a novel approach to concurrently address these challenges by using the unique properties of polybenzoxazine (pBO) polymers, namely near‐zero shrinkage and high residual‐char yield even after pyrolysis at high temperatures. Pyrolysis of a nanocubic prussian blue analogue precursor (KmMnx[Co(CN)6]y⋅n H2O) embedded in a bisphenol A and aniline‐based pBO led to the formation of a N‐doped carbon matrix modified with MnxCoyOz nanocubes. The obtained electrocatalyst exhibits high efficiency toward the oxygen evolution reaction (OER) and more importantly a stable performance for at least 65 h.
Seed dispersal of Diospyros virginiana in the past and the present: Evidence for a generalist evolutionary strategy
Authors: Rebein Mimi , Davis Charli N. , Abad Helena , Stone Taylor , del Sol Jillian , Skinner Natalie , Moran Matthew D. 
Published: May 2017

AbstractSeveral North American trees are hypothesized to have lost their co‐evolved seed disperser during the late‐Pleistocene extinction and are therefore considered anachronistic. We tested this hypothesis for the American persimmon (Diospyros virginiana) by studying the effects of gut passage of proposed seed dispersers on seedling survival and growth, natural fruiting characteristics, and modern animal consumption patterns. We tested gut passage effects on persimmon seeds using three native living species, the raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), and coyote (Canis latrans), and two Pleistocene analogs; the Asian elephant (Elephas maximus) and alpaca (Vicugna pacos). Persimmon seeds excreted by raccoons, coyotes, and elephants survived gut transit. Gut passage did not affect sprouting success, but did tend to decrease time to sprout and increase seedling quality. Under field conditions, persimmon fruits were palatable on the parent tree and on the ground for an equal duration, but most fruits were consumed on the ground. Seven vertebrate species fed upon persimmon fruits, with the white‐tailed deer (Odocoileus virginianus)—a species not capable of dispersing persimmon seeds—comprising over 90% of detections. Conversely, potential living seed dispersers were rarely detected. Our results suggest the American persimmon evolved to attract a variety of seed dispersers and thus is not anachronistic. However, human‐induced changes in mammal communities could be affecting successful seed dispersal. We argue that changes in the relative abundance of mammals during the Anthropocene may be modifying seed dispersal patterns, leading to potential changes in forest community composition.
A global study of GPP focusing on light‐use efficiency in a random forest regression model
Authors: Wei Suhua , Yi Chuixiang , Fang Wei , Hendrey George 
Published: May 2017

AbstractLight‐use efficiency (LUE) is at the core of mechanistic modeling of global gross primary production (GPP). However, most LUE estimates in global models are satellite based and coarsely measured with emphasis on environmental variables. Others are from eddy covariance towers with much greater spatial and temporal data quality and emphasis on mechanistic processes, but in a limited number of sites. In this study, we conducted a comprehensive global study of tower‐based LUE from 237 FLUXNET towers, and scaled up LUEs from in situ tower level to global biome level. We integrated the tower‐based LUE estimates with key environmental and biological variables at 0.5° × 0.5° grid‐cell resolutions, using a random forest regression (RFR) approach. Then, we developed a RFR‐LUE‐GPP model using the grid‐cell LUE data. In order to calibrate the LUE model, we developed a data‐driven RFR‐GPP model using RFR method only. Our results showed LUE varies largely with latitude. We estimated a global area‐weighted average of LUE at 1.23 ± 0.03 g C·m−2·MJ−1 APAR, which led to an estimate of global GPP of 107.5 ± 2.5 Gt C/yr from 2001 to 2005. Large uncertainties existed in GPP estimations over sparsely vegetated areas covered by savannas and woody savannas at middle to low latitude (i.e., 20° S–40° S and 5° N–40° N) due to the lack of available data. Model results were improved by incorporating Köppen climate types to represent climate/meteorological information in machine‐learning modeling. This brought a new understanding to the recognized problem of climate dependence of spring onset of photosynthesis and the challenges in accurately modeling the biome GPP of evergreen broadleaf forests (EBF). The divergent responses of GPP to temperature and precipitation at middle to high latitudes and at middle to low latitudes echo the necessity of modeling GPP separately by latitudes.