bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interfacial Super‐Assembled Porous CeO2/C Frameworks Featuring Efficient and Sensitive Decomposing Li2O2 for Smart Li–O2 Batteries
Authors: Hou Yue , Wang Jun , Liu Jiaqing , Hou Chuanxin , Xiu Zhaohong , Fan Yuqi , Zhao Lanling , Zhai Yanjie , Li Hongyu , Zeng Jie , Gao Xiang , Zhou Shan , Li Dongwei , Li Yong , Dang Feng , Liang Kang , Chen Pu , Li Changming , Zhao Dongyuan , Kong Biao 
Published: September 2019

AbstractThe Li–O2 battery (LOB) represents a promising candidate for future electric vehicles owing to its outstanding energy density. However, the practical application of LOB cells is largely blocked by the poor cycling performance of cathode materials. Herein, an ultralong 440‐cycle life of an LOB cell is achieved using CeO2 nanocubes super‐assembled on an inverse opal carbon matrix as the cathode material without any additives. CeO2 is proved to be effective for the complete and sensitive decomposition of loosely stacked Li2O2 films during the oxygen evolution reaction process and full accommodation of volume changes caused by the fast growth of Li2O2 films during the oxygen reduction reaction process. The super‐assembled porous CeO2/C frameworks satisfy critical requirements including controlled size, morphology, high Ce3+/Ce4+ ratio, and efficient volume change accommodation, which dramatically increase the cycle life of LOB cell to 440 cycles. This study reveals the design strategy for high performance CeO2 catalyst cathodes for LOB cells and the generation mechanisms of Li2O2 films during the discharge process by using density functional theory calculations, showing new avenues for improving the future smart design of CeO2‐based cathode catalysts for Li–O2 batteries.
Surface Engineering of 3D Gas Diffusion Electrodes for High‐Performance H2 Production with Nonprecious Metal Catalysts
Authors: Sanchez Joel , Hellstern Thomas R. , King Laurie A. , Jaramillo Thomas F. 
Published: September 2019

AbstractIn this work, a methodology is demonstrated to engineer gas diffusion electrodes for nonprecious metal catalysts. Highly active transition metal phosphides are prepared on carbon‐based gas diffusion electrodes with low catalyst loadings by modifying the O/C ratio at the surface of the electrode. These nonprecious metal catalysts yield extraordinary performance as measured by low overpotentials (51 mV at −10 mA cm−2), unprecedented mass activities (>800 A g−1 at 100 mV overpotential), high turnover frequencies (6.96 H2 s−1 at 100 mV overpotential), and high durability for a precious metal‐free catalyst in acidic media. It is found that a high O/C ratio induces a more hydrophilic surface directly impacting the morphology of the CoP catalyst. The improved hydrophilicity, stemming from introduced oxyl groups on the carbon electrode, creates an electrode surface that yields a well‐distributed growth of cobalt electrodeposits and thus a well‐dispersed catalyst layer with high surface area upon phosphidation. This report demonstrates the high‐performance achievable by CoP at low loadings which facilitates further cost reduction, an important part of enabling the large‐scale commercialization of non‐platinum group metal catalysts. The fabrication strategies described herein offer a pathway to lower catalyst loading while achieving high efficiency and promising stability on a 3D electrode.
Nonlinear modeling of saguaro growth rates reveals the importance of temperature for size‐dependent growth
Authors: Félix‐Burruel Ricardo E. , Larios Eugenio , Bustamante Enriquena , Búrquez Alberto 
Published: September 2019

PremiseThe saguaro cactus is an iconic species of the Sonoran Desert. Its individual growth rates have been investigated for over 100 years. Its growth dynamics have been studied using phenomenological models intended to estimate growth, but not to understand the underlying biological processes. Most studies have suggested summer rainfall as the sole factor determining saguaro growth, overlooking the influence of other factors related to the process of growth.MethodsWe analyzed the annual growth rates for 13 saguaro populations in the Sonoran Desert using nonlinear models. These are better suited to analyze growth since they consider the fact that maximum growth rates diminish just before the onset of reproduction. We related model parameters to the local climate.ResultsThe most parsimonious model was the Ricker function that described growth considering cactus decline with age. Variance in temperature, rather than precipitation, was more closely related to growth. Higher variance in temperature at the beginning of the warm season was detrimental to saguaro growth.ConclusionsSimple nonlinear equations modeled growth rate using biologically interpretable parameters related to climate factors. Because the temperature is projected to increase in both mean and variance by climate change, the population dynamics of this iconic cactus are likely to be affected.
The onset of xylogenesis in Smith fir is not related to outer bark thickness
Authors: Li Xiaoxia , Rossi Sergio , Liang Eryuan 
Published: September 2019

PremiseThe resumption of stem growth varies across the ontogenetic development of trees. Compared with younger trees, older ones have thicker outer bark with a temperature‐insulating effect that could potentially prevent the stem from warming in the spring. However, the question of whether xylogenesis in old trees is influenced by the thick bark still remains unresolved.MethodsWe investigated the onset of xylogenesis across the ontogenetic development of Smith fir (Abies georgei var. smithii) trees in the Sygera Mountains, southeastern Tibetan Plateau. The outer bark of older trees was also removed. Xylogenesis was monitored in microcores we collected every 3 days during May and June in 2017.ResultsXylogenesis began in late May in young (<50 yr) and mature (50–100 yr) trees, 1 week earlier than in adult (>100–150 yr) and old (>150–200 yr) trees. Older (>200 yr) trees had the latest onset of xylogenesis, 2 weeks after young trees. The resumption of xylogenesis was similar between the control and bark‐removed trees.ConclusionsGrowth resumption was delayed in older and bigger trees. Outer bark did not affect the onset of xylogenesis, which indicated that the delayed resumption of growth during the lifespan of trees could be more related to endogenous factors than to an insulating effect of the thick bark of older individuals.
Odontogenic sinusitis is a common cause of unilateral sinus disease with maxillary sinus opacification
Authors: Turfe Zaahir , Ahmad Abid , Peterson Edward I. , Craig John R. 
Published: September 2019

BackgroundUnilateral sinus disease (USD) carries a broader differential diagnosis than bilateral sinus disease, including various inflammatory and neoplastic conditions. Odontogenic sinusitis (ODS) is a common cause of unilateral maxillary sinusitis, but few studies have examined its incidence among all USD etiologies. The main purposes of this prospective study were to determine the incidences of ODS and other etiologies causing USD with complete maxillary sinus opacification on computed tomography (CT), and to compare CT features of ODS and non‐odontogenic USD patients. In addition, clinical features of the ODS cohort are described.MethodsA prospective case series of 134 patients with USD with complete maxillary sinus opacification on CT was conducted from August 2015 to November 2018. Based on nasal endoscopy, sinus CT, and dental examination and imaging, patients were categorized as having unilateral ODS or non‐odontogenic USD. Patients with non‐odontogenic USD were categorized as inflammatory or neoplastic. Demographic and clinical data were reported for ODS patients.ResultsOf the 134 patients, 45% had ODS, 36% had non‐odontogenic inflammatory conditions, 17% had inverted papilloma, and 2% had malignancies. Of the 60 ODS cases, 86.7% were associated with middle meatal purulence on nasal endoscopy. On CT, 88.3% had extramaxillary sinus disease extension, and 65.5% of CT reports made no mention of dental pathology.ConclusionODS caused nearly 50% of all USD cases with maxillary sinus opacification on CT, and was the most common individual etiology. ODS was frequently associated with anterior ethmoid and frontal sinus disease on CT, and middle meatal purulence on nasal endoscopy.
Defect‐Mediated Ordering of Condensed Water Structures in Microporous Zeolites
Authors: Bukowski Brandon C. , Bates Jason S. , Gounder Rajamani , Greeley Jeffrey 
Published: September 2019

AbstractAb‐initio molecular dynamics simulations and transmission infrared spectroscopy are employed to characterize the structure of water networks in defect‐functionalized microporous zeolites. Thermodynamically stable phases of clustered water molecules are localized at some of the defects in zeolite Beta, which include catalytic sites such as framework Lewis acidic Sn atoms in closed and hydrolyzed‐open forms, as well as silanol nests. These water clusters compete with ideal gas‐like structures at low water densities and pore‐filling phases at higher water densities, with the equilibrium phase determined by the water chemical potential. The physical characteristics of these phases are determined by the defect identity, with the local binding and orientation of hydroxyl moieties around the defects playing a central role. The results suggest general principles for how the structure of polar solvents in microporous solid acids is influenced by local defect functionalization, and the thermodynamic stability of the condensed phases surrounding such sites, in turn, implies that the catalysis of Lewis acids will be influenced by local water ordering.
Selective Catalytic Chemistry at Rhodium(II) Nodes in Bimetallic Metal–Organic Frameworks
Authors: Shakya Deependra M. , Ejegbavwo Otega A. , Rajeshkumar Thayalan , Senanayake Sanjaya D. , Brandt Amy J. , Farzandh Sharfa , Acharya Narayan , Ebrahim Amani M. , Frenkel Anatoly I. , Rui Ning , Tate Gregory L. , Monnier John R. , Vogiatzis Konstantinos D. , Shustova Natalia B. , Chen Donna A. 
Published: September 2019

AbstractWe report the first study of a gas‐phase reaction catalyzed by highly dispersed sites at the metal nodes of a crystalline metal–organic framework (MOF). Specifically, CuRhBTC (BTC3−=benzenetricarboxylate) exhibited hydrogenation activity, while other isostructural monometallic and bimetallic MOFs did not. Our multi‐technique characterization identifies the oxidation state of Rh in CuRhBTC as +2, which is a Rh oxidation state that has not previously been observed for crystalline MOF metal nodes. These Rh2+ sites are active for the catalytic hydrogenation of propylene to propane at room temperature, and the MOF structure stabilizes the Rh2+ oxidation state under reaction conditions. Density functional theory calculations suggest a mechanism in which hydrogen dissociation and propylene adsorption occur at the Rh2+ sites. The ability to tailor the geometry and ensemble size of the metal nodes in MOFs allows for unprecedented control of the active sites and could lead to significant advances in rational catalyst design.
Über bislang nicht beachtete Parallelen in der Reaktivität von Arinen und Donor‐Akzeptor‐Cyclopropanen
Authors: Werz Daniel B. , Biju Akkattu T. 
Published: September 2019

AbstractArine und Donor‐Akzeptor‐substituierte (D‐A‐)Cyclopropane sind zwei Klassen gespannter Systeme mit einer Vielzahl an möglichen Anwendungen in der organischen Synthese. In den letzten beiden Jahrzehnten hat die Chemie dieser beiden Spezies eine Renaissance erlebt, vor allem wegen der milden und zuverlässigen Methoden zu ihrer Herstellung oder Aktivierung. In der Regel führen Arine als leicht polarisierbare Systeme zur 1,2‐Disubstitution, während D‐A‐Cyclopropane als polarisierte Systeme zur 1,3‐Disubstitution neigen und dabei auffällige Ähnlichkeiten aufweisen. Die Umsetzungen mit 1,2‐ und 1,3‐Dipolen führen zu cyclischen Strukturen. Die mit Arinen entstehenden viergliedrigen cyclischen Intermediate können weiterreagieren, während die analogen fünfgliedrigen Cyclen hervorgehend aus D‐A‐Cyclopropanen meist die finalen Endprodukte darstellen. Es gibt jedoch einige Fälle, in denen sich diese Zwischenprodukte überraschend unterschiedlich verhalten. Dieser Kurzaufsatz zielt darauf ab, die Parallelen in der Reaktivität von Arinen und D‐A‐Cyclopropanen aufzuzeigen und somit Licht auf die bisher vernachlässigten Ähnlichkeiten dieser beiden reaktiven Spezies zu werfen.
Bifunctional Metal Nanocrystals for Catalyzing and Reporting on Chemical Reactions
Authors: Shi Shi , Qin Dong 
Published: September 2019

AbstractBifunctional nanocrystals with integrated plasmonic and catalytic activities hold great promise for analyzing chemical reactions by in situ surface‐enhanced Raman spectroscopy. This Minireview gives a brief introduction to the general strategies for designing such nanocrystals, followed by four typical examples, including their fabrication, characterization, and potential limitation. We then use the reduction of 4‐nitrothiophenol and oxidation of 4‐aminothiophenol as two model systems to demonstrate the capabilities of these bifunctional nanocrystals to monitor chemical reactions for the elucidation of reaction mechanisms and measurement of kinetics. We conclude with perspectives on further development of these bifunctional nanocrystals into a viable platform for investigating other types of catalytic reactions.
Loading‐Dependent Structural Model of Polymeric Micelles Encapsulating Curcumin by Solid‐State NMR Spectroscopy
Authors: Pöppler Ann‐Christin , Lübtow Michael M. , Schlauersbach Jonas , Wiest Johannes , Meinel Lorenz , Luxenhofer Robert 
Published: September 2019

AbstractDetailed insight into the internal structure of drug‐loaded polymeric micelles is scarce, but important for developing optimized delivery systems. We observed that an increase in the curcumin loading of triblock copolymers based on poly(2‐oxazolines) and poly(2‐oxazines) results in poorer dissolution properties. Using solid‐state NMR spectroscopy and complementary tools we propose a loading‐dependent structural model on the molecular level that provides an explanation for these pronounced differences. Changes in the chemical shifts and cross‐peaks in 2D NMR experiments give evidence for the involvement of the hydrophobic polymer block in the curcumin coordination at low loadings, while at higher loadings an increase in the interaction with the hydrophilic polymer blocks is observed. The involvement of the hydrophilic compartment may be critical for ultrahigh‐loaded polymer micelles and can help to rationalize specific polymer modifications to improve the performance of similar drug delivery systems.
Hydrothermal liquefaction of macroalgae for the production of renewable biofuels
Authors: Raikova Sofia , Allen Michael J. , Chuck Christopher J. 
Published: September 2019

AbstractIn all biorefinery systems, excess water represents a key challenge, and its removal by drying is often a necessary and crucial pre‐treatment. Second‐generation feedstocks have often fallen at this hurdle, particularly microalgae‐derived biomasses, which require extensive (and costly) dewatering. Hydrothermal liquefaction (HTL) has gained increasing attention in recent years as a technology that uses the water present in the feedstock as a versatile reaction medium, which functions as a solvent, reactant, and catalyst for a cascade of organic reactions. Converting organic biomasses into oil, aqueous, solid, and gas fractions, the development of HTL provides the opportunity to exploit previously unsuitable biomasses in a versatile bio‐refinery approach. Marine macroalgae (seaweeds) offer a sustainable source of renewable biomass, which require no land or freshwater to cultivate or harvest. With 70% of the surface of the planet covered in seawater and levels of eutrophication increasing, seaweeds are an underutilized resource with excellent potential for relieving the pressure on fossil resources. Hitherto, this exploitation has been hindered by a lack of suitable and economical processing tools. Here we review the potential for applying HTL to processing marine macroalgae and discuss the potential products and services that can be derived from this potential biorefinery system. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.
Thermostability enhancement of the Pseudomonas fluorescens esterase I by in vivo folding selection in Thermus thermophilus
Authors: Mate Diana M. , Rivera Noé R. , Sanchez‐Freire Esther , Ayala Juan A. , Berenguer José , Hidalgo Aurelio 
Published: September 2019

AbstractProlonged stability is a desired property for the biotechnological application of enzymes since it allows its reutilization, contributing to making biocatalytic processes more economically competitive with respect to chemical synthesis. In this study, we have applied selection by folding interference at high temperature in Thermus thermophilus to obtain thermostable variants of the esterase I from Pseudomonas fluorescens (PFEI). The most thermostable variant (Q11L/A191S) showed a melting temperature (Tm) of 77.3 ± 0.1°C (4.6°C higher than the wild‐type) and a half‐life of over 13 hr at 65°C (7.9‐fold better than the wild‐type), with unchanged kinetic parameters. Stabilizing mutations Q11L and A191S were incorporated into PFEI variant L30P, previously described to be enantioselective in the hydrolysis of the (−)‐enantiomer of the Vince lactam. The final variant Q11L/L30P/A191S showed a significant improvement in thermal stability (Tm of 80.8 ± 0.1°C and a half‐life of 65 min at 75°C), while retaining enantioselectivity (E > 100). Structural studies revealed that A191S establishes a hydrogen bond network between a V‐shaped hairpin and the α/β hydrolase domain that leads to higher rigidity and thus would contribute to explaining the increase in stability.
Optimization of the Cellulase−Ultrasonic Synergistic Extraction Conditions of Polysaccharides from Lenzites betulina
Authors: Guo Lei , Tan Da‐Cong , Hui Fu‐Yi , Gu Fan , Xiao Kun‐Min , Hua Yan 
Published: September 2019

AbstractLenzites betulina has been recognized as a rich source of chemical components, including polysaccharides, sterides and sugar alcohols. In this study, cellulase−ultrasonic synergistic extraction method was applied to extract polysaccharides from L. betulina, and the response surface methodology was used to optimize the extraction conditions. The eight basic factors affecting extraction yield were evaluated by Plackett−Burman design (PBD). Then, the four important factors significantly affecting the yield of polysaccharides from L. betulina, including enzymolysis temperature, enzymolysis time, ultrasound time and ultrasound temperature, were optimized by Box−Behnken design (BBD). Maximum extraction yield of L. betulina polysaccharides was 13.64±0.09 % at a cellulase dosage of 0.8 %, enzymolysis temperature of 60 °C, enzymolysis time of 180 min, pH of 4.5, liquid‐solid ratio of 45 ml/g, ultrasound power of 300 W, ultrasound time of 20 min and ultrasound temperature of 45 °C. Subsequently, the characteristic structure of crude polysaccharides was determined by FT‐IR. Results indicated that cellulase−ultrasonic synergistic treatment is suitable for L. betulina polysaccharides extraction, and it has good prospect for development and utilization.
Influence of Carbon Coating on Intercalation Kinetics and Transport Properties of LiFePO4
Authors: Iarchuk Anna R. , Nikitina Victoria A. , Karpushkin Evgeny A. , Sergeyev Vladimir G. , Antipov Evgeny V. , Stevenson Keith J. , Abakumov Artem M. 
Published: September 2019

AbstractWe report on a comparative study of Li+ intercalation kinetics for LiFePO4 materials with polydopamine‐derived and glucose‐derived carbon coatings. We demonstrate that the uniform polydopamine‐derived carbon coating affects the charge transfer rates and transport properties (electronic conductivity) of composite electrodes only slightly (compared to the inhomogeneous glucose‐derived coatings), whereas much more pronounced effects are observed for the apparent diffusion coefficients and nucleation barriers. Thick and uniform carbon surface layers cause a sharp decrease in the ionic diffusion coefficients, which results in the loss of capacity at higher charge/discharge rates for LiFePO4 composite electrodes. The new phase nucleation rates are also demonstrated to decrease significantly for the samples with thicker coatings inducing higher potential differences between charge and discharge curves. The analysis of the rate determining factors for the LiFePO4 electrodes points to the rate limitations induced by the slow nucleation and slow ionic diffusion, whereas the formation of a polydopamine‐derived uniform carbon layer tends to hinder the (de)intercalation reaction and does not provide additional benefits compared to glucose‐derived carbon coatings comprising conductive yet inhomogeneous layers.
Azo‐Group‐Containing Organic Compounds as Electrode Materials in Full‐Cell Lithium‐Ion Batteries
Authors: Wang Yingqian , Yang Zhixiong , Xia Tianlai , Pan Guangxing , Zhang Ling , Chen Hong , Zhang Jiaheng 
Published: September 2019

AbstractInorganic compounds, including graphite, transition metal oxides, and chalcogenides, are widely used as electrode materials in rechargeable lithium‐ion batteries (LIBs). However, environmentally friendly and cost‐effective alternatives are pursued by focusing on the molecular design of organic materials that could be potential electrode materials in next‐generation LIBs. Herein, we study the utilization of an organic compound, azobenzene 4,4‐dicarboxylate lithium (ADL), as a negative electrode in full‐cell LIBs. The full‐cell LIBs are assembled by using ADL as the negative electrode, LiCoO2 (LCO/ADL) or LiFePO4 (LFP/ADL) as the positive electrode, and 1 M LiPF6 dissolved in ethylene carbonate/diethylene carbonate (EC : DEC=1 : 1 by volume) as the electrolyte. Then, ex situ X‐ray diffraction (XRD), ex situ X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were carried out to understand the charge storage mechanism and structural changes during the electrochemical reaction. From the charge/discharge measurements, LFP/ADL rendered a higher specific capacity retention (88.05 %) than LCO/ADL full‐cells (73.79 %) after 200 cycles at a current density of 100 mA g−1. The XPS analysis revealed that the deposition of metallic Li on the ADL anode in LCO/ADL full‐cells led to rapid capacity decay and inferior cyclic performance, whereas Li‐free metal deposition had been observed on the ADL anode in LFP/ADL full cells, which explained the higher cyclic stability and capacity retention rate in LFP/ADL full‐cells. The present study provides useful insights into the development and practical utilization of organic electrodes in next‐generation Li‐ion battery technology.
Chemical Synthesis of Magnetic Nanoparticles for Permanent Magnet Applications
Authors: Shen Bo , Sun Shouheng 
Published: September 2019

AbstractPermanent magnets are a class of critical materials for information storage, energy storage, and other magneto‐electronic applications. Compared with conventional bulk magnets, magnetic nanoparticles (MNPs) show unique size‐dependent magnetic properties, which make it possible to control and optimize their magnetic performance for specific applications. The synthesis of MNPs has been intensively explored in recent years. Among different methods developed thus far, chemical synthesis based on solution‐phase reactions has attracted much attention owing to its potential to achieve the desired size, morphology, structure, and magnetic controls. This Minireview focuses on the recent chemical syntheses of strongly ferromagnetic MNPs (Hc>10 kOe) of rare‐earth metals and FePt intermetallic alloys. It further discusses the potential of enhancing the magnetic performance of MNP composites by assembly of hard and soft MNPs into exchange‐coupled nanocomposites. High‐performance nanocomposites are key to fabricating super‐strong permanent magnets for magnetic, electronic, and energy applications.