bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanostructuring Noble Metals as Unsupported Electrocatalysts for Polymer Electrolyte Fuel Cells
Authors: Cai Bin , Henning Sebastian , Herranz Juan , Schmidt Thomas J. , Eychmüller Alexander 
Published: August 2017

AbstractTwo major challenges that impede fuel cell technology breakthrough are the insufficient activity of the electrocatalysts for the oxygen reduction reaction and their degradation during operation, caused by the potential‐induced corrosion of their carbon‐support upon fuel cell operation. Unsupported electrocatalysts derived from tailored noble‐metal nanostructures are superior to the conventional carbon‐supported Pt nanoparticle catalysts and address these barriers by fine‐tuning the surface composition and eliminating the support. Herein, recent efforts and achievements in the design, synthesis and characterization of unsupported electrocatalysts are reviewed, paying special attention to noble‐metal aerogels, nano/meso‐structured thin films and template‐derived metal nanoarchitectures. Their electrocatalytic performances for oxygen reduction are compared and discussed, and examples of successful catalyst transfer to polymer electrolyte fuel cells are highlighted. This report aims to demonstrate the potential and challenges of implementing unsupported catalysts in fuel cells, thereby providing a perspective on the further development of these materials.
Post Iron Decoration of Mesoporous Nitrogen‐Doped Carbon Spheres for Efficient Electrochemical Oxygen Reduction
Authors: Liu Zhuang , Sun Fei , Gu Lin , Chen Gen , Shang Tongtong , Liu Jing , Le Zaiyuan , Li Xianyang , Wu Hao Bin , Lu Yunfeng 
Published: August 2017

AbstractIron–nitrogen–carbon (Fe–N–C) catalysts are considered as the most promising nonprecious metal catalysts for oxygen reduction reactions (ORRs). Their synthesis generally involves complex pyrolysis reactions at high temperature, making it difficult to optimize their composition, pore structure, and active sites. This study reports a simple synthesis strategy by reacting preformed nitrogen‐doped carbon scaffolds with iron pentacarbonyl, a liquid precursor that can effectively form active sites with the nitrogen sites, enabling more effective control of the catalyst. The resultant catalyst possesses a well‐defined mesoporous structure, a high surface area, and optimized active sites. The catalysts exhibit high ORR activity comparable to that of Pt/C catalyst (40% Pt loading) in alkaline media, with excellent stability and methanol tolerance. The synthetic strategy can be extended to synthesize other metal–N–C catalysts.
Surface Free Energy‐Induced Assembly to the Synthesis of Grid‐Like Multicavity Carbon Spheres with High Level In‐Cavity Encapsulation for Lithium–Sulfur Cathode
Authors: Zhang Lu‐Hua , He Bin , Li Wen‐Cui , Lu An‐Hui 
Published: August 2017

AbstractCarbon microcapsules with a large interior cavity and porous shell are ideal hosts for guest species, while to maximize in‐cavity volume has always been a challenge. Herein, a surface free energy‐induced assembly approach is proposed for synthesis of multicavity carbon spheres (MCC). When used as a host for lithium–sulfur cathodes, MCC are fully accessible for sulfur—with high level in‐cavity encapsulation ability of grid‐like cavities. The crucial point for this assembly approach is the employment of small sized nanoemulsions with high homogeneity as primary building blocks. Spontaneous aggregation and assembly of substructural units are processing in following hydrothermal synthesis induced by reduction of surface free energy of system. As a result, multicavity structure is formed, where the size and number of cavities can be modulated by changing size of nanoemulsion and concentration of polymer. Confined pyrolysis enables to further enlarge cavity size compared to regular pyrolysis. The carbon–sulfur cathode exhibits excellent cycling stability and rate performance, i.e., high capacity of 943 and 869 mA h g−1 after 200 cycles at current density of 0.5 and 2.0 C. The strategy has paved the way for custom‐ordered synthesis of nanostructured carbon with keen demands in high loading capacity of guest species.
Two‐Dimensional Calix[4]arene‐based Metal–Organic Coordination Networks of Tunable Crystallinity
Authors: Moradi Mina , Tulli Ludovico G. , Nowakowski Jan , Baljozovic Milos , Jung Thomas A. , Shahgaldian Patrick 
Published: August 2017

AbstractA flexible and versatile method to fabricate two‐dimensional metal–organic coordination networks (MOCNs) by bottom‐up self‐assembly is described. 2D crystalline layers were formed at the air–water interface, coordinated by ions from the liquid phase, and transferred onto a solid substrate with their crystallinity preserved. By using an inherently three‐dimensional amphiphile, namely 25,26,27,28‐tetrapropoxycalix[4]arene‐5,11,17,23‐tetracarboxylic acid, and a copper metal node, large and monocrystalline dendritic MOCN domains were formed. The method described allows for the fabrication of monolayers of tunable crystallinity on liquid and solid substrates. It can be applied to a large range of differently functionalized organic building blocks, also beyond macrocycles, which can be interconnected by diverse metal nodes.
Malonic Acid Diazoesters for C−H Insertion Crosslinking (CHic) Reactions: A Versatile Method for the Generation of Tailor‐Made Surfaces
Authors: Kotrade Philip F. , Rühe Jürgen 
Published: August 2017

AbstractA simple and versatile method for the modification of a broad spectrum of surfaces with thin polymer films through the thermally or photochemically induced generation of surface‐attached polymer networks is reported. The system is based on copolymers containing diazomalonate groups, which can be activated by heat or light. To this end, the copolymers are deposited from solution onto solid substrates by standard techniques of thin‐film deposition (spin coating, dip coating). Upon activation the diazomalonate group decomposes and forms a carbene, which induces C−H insertion crosslinking (CHic) reactions. In the course of this process network formation and covalent surface attachment occur at the same time. The crosslinking process proceeds very rapidly, especially when the carbenes generated in the activation process cannot undergo Wolff‐rearrangement. The presented system can be used for the generation of a wide range of polymer layers and microstructures on a broad spectrum of surfaces.
HKOH‐1: A Highly Sensitive and Selective Fluorescent Probe for Detecting Endogenous Hydroxyl Radicals in Living Cells
Authors: Bai Xiaoyu , Huang Yueyang , Lu Mingyang , Yang Dan 
Published: August 2017

AbstractThe hydroxyl radical (.OH), one of the most reactive and deleterious reactive oxygen species (ROS), has been suggested to play an essential role in many physiological and pathological scenarios. However, a reliable and robust method to detect endogenous .OH is currently lacking owing to its extremely high reactivity and short lifetime. Herein we report a fluorescent probe HKOH‐1 with superior in vitro selectivity and sensitivity towards .OH. With this probe, we have calibrated and quantified the scavenging capacities of a wide range of reported .OH scavengers. Furthermore, HKOH‐1r, which was designed for better cellular uptake and retention, has performed robustly in detection of endogenous .OH generation by both confocal imaging and flow cytometry. Furthermore, this probe has been applied to monitor .OH generation in HeLa cells in response to UV light irradiation. Therefore, HKOH‐1 could be used for elucidating .OH related biological functions.
Iron‐Catalyzed anti‐Selective Carbosilylation of Internal Alkynes
Authors: Iwamoto Takahiro , Nishikori Tatsushi , Nakagawa Naohisa , Takaya Hikaru , Nakamura Masaharu 
Published: August 2017

AbstractReported is the anti‐selective carbosilylation of internal alkynes with silylborane and alkyl halides using a FeBr2/DPPE catalyst system. The iron catalyst allows simultaneous introduction of a carbon electrophile and a silicon nucleophile to simple internal alkynes, including diaryl‐, dialkyl‐, and aryl/alkyl‐substituted alkynes, in a highly stereoselective manner. Alkyl halides are applicable as the electrophiles, thereby enabling the synthesis of a variety of tetrasubstituted alkenylsilanes. In addition, syn‐selective carbosilylation was achieved through stereoswitching, by using a silylborane having oxygen functionality on the silyl group. This novel iron‐catalyzed carbosilylation is a useful tool for expedient synthesis of stereodefined multisubstituted olefins, a fundamental structural motif in organic chemistry.
Fluorine Pseudocontact Shifts Used for Characterizing the Protein–Ligand Interaction Mode in the Limit of NMR Intermediate Exchange
Authors: Gao Jia , Liang E , Ma Rongsheng , Li Fudong , Liu Yixiang , Liu Jiuyang , Jiang Ling , Li Conggang , Dai Haiming , Wu Jihui , Su Xuncheng , He Wei , Ruan Ke 
Published: August 2017

AbstractThe characterization of protein–ligand interaction modes becomes recalcitrant in the NMR intermediate exchange regime as the interface resonances are broadened beyond detection. Here, we determined the 19F low‐populated bound‐state pseudocontact shifts (PCSs) of mono‐ and di‐fluorinated inhibitors of the BRM bromodomain using a highly skewed protein/ligand ratio. The bound‐state 19F PCSs were retrieved from 19F chemical exchange saturation transfer (CEST) in the presence of the lanthanide‐labeled protein, which was termed the 19F PCS‐CEST approach. These PCSs enriched in spatial information enabled the identification of best‐fitting poses, which agree well with the crystal structure of a more soluble analog in complex with the BRM bromodomain. This approach fills the gap of the NMR structural characterization of lead‐like inhibitors with moderate affinities to target proteins, which are essential for structure‐guided hit‐to‐lead evolution.
Efficient Aryl Migration from an Aryl Ether to a Carboxylic Acid Group To Form an Ester by Visible‐Light Photoredox Catalysis
Authors: Wang Shao‐Feng , Cao Xiao‐Ping , Li Yang 
Published: August 2017

AbstractWe have developed a highly efficient aryl migration from an aryl ether to a carboxylic acid group through retro‐Smiles rearrangement by visible‐light photoredox catalysis at ambient temperature. Transition metals and a stoichiometric oxidant and base are avoided in the transformation. Inspired by the high efficiency of this transformation and the fundamental importance of C−O bond cleavage, we developed a novel approach to the C−O cleavage of a biaryl ether to form two phenolic compounds, as demonstrated by a one‐pot, two‐step gram‐scale reaction under mild conditions. The aryl migration exhibits broad scope and can be applied to the synthesis of pharmaceutical compounds, such as guacetisal. Primary mechanistic studies indicate that the catalytic cycle occurs by a reductive quenching pathway.
Valence Interconversion of Octahedral Nickel(II/III/IV) Centers
Authors: Kouno Masahiro , Yoshinari Nobuto , Kuwamura Naoto , Yamagami Kohei , Sekiyama Akira , Okumura Mitsutaka , Konno Takumi 
Published: August 2017

AbstractThree oxidation states (+2, +3, +4) of an octahedral nickel center were stabilized in a newly prepared RhNiRh trinuclear complex, [Ni{Rh(apt)3}2]n+ (apt=3‐ aminopropanethiolate), in which the nickel center was bound by six thiolato donors sourced from two redox‐inert fac‐[RhIII(apt)3] octahedral units. The three oxidation states of the octahedral nickel center were fully characterized by single‐crystal X‐ray crystallography, as well as spectroscopic, electrochemical, and magnetic measurements; all three were interconvertible, and the conversion was accompanied by changes in color, magnetism, and Jahn–Teller distortion.
The Safety and Immunogenicity of Live Zoster Vaccination in Patients With Rheumatoid Arthritis Before Starting Tofacitinib: A Randomized Phase II Trial
Authors: Winthrop Kevin L. , Wouters Ann G. , Choy Ernest H. , Soma Koshika , Hodge Jennifer A. , Nduaka Chudy I. , Biswas Pinaki , Needle Elie , Passador Sherry , Mojcik Christopher F. , Rigby William F. 
Published: August 2017

ObjectivePatients with rheumatoid arthritis (RA) are at increased risk of herpes zoster, and vaccination is recommended for patients ages 50 years and older, prior to starting treatment with biologic agents or tofacitinib. Tofacitinib is an oral JAK inhibitor for the treatment of RA. We evaluated its effect on the immune response and safety of live zoster vaccine (LZV).MethodsIn this phase II, 14‐week, placebo‐controlled trial, patients ages 50 years and older who had active RA and were receiving background methotrexate were given LZV and randomized to receive tofacitinib 5 mg twice daily or placebo 2–3 weeks postvaccination. We measured humoral responses (varicella zoster virus [VZV]–specific IgG level as determined by glycoprotein enzyme‐linked immunosorbent assay) and cell‐mediated responses (VZV‐specific T cell enumeration, as determined by enzyme‐linked immunospot assay) at baseline and 2 weeks, 6 weeks, and 14 weeks postvaccination. End points included the geometric mean fold rise (GMFR) in VZV‐specific IgG levels (primary end point) and T cells (number of spot‐forming cells/106 peripheral blood mononuclear cells) at 6 weeks postvaccination.ResultsOne hundred twelve patients were randomized to receive tofacitinib (n = 55) or placebo (n = 57). Six weeks postvaccination, the GMFR in VZV‐specific IgG levels was 2.11 in the tofacitinib group and 1.74 in the placebo group, and the VZV‐specific T cell GMFR was similar in the tofacitinib group and the placebo group (1.50 and 1.29, respectively). Serious adverse events occurred in 3 patients in the tofacitinib group (5.5%) and 0 patients (0.0%) in the placebo group. One patient, who lacked preexisting VZV immunity, developed cutaneous vaccine dissemination 2 days after starting tofacitinib (16 days postvaccination). This resolved after tofacitinib was discontinued and the patient received antiviral treatment.ConclusionPatients who began treatment with tofacitinib 2–3 weeks after receiving LZV had VZV‐specific humoral and cell‐mediated immune responses to LZV similar to those in placebo‐treated patients. Vaccination appeared to be safe in all of the patients except 1 patient who lacked preexisting VZV immunity.
Anschlüsse für den Holzbau mit Polymerverguss
Authors: Jahreis Markus , Oppel Mike , Rautenstrauch Karl 
Published: August 2017

AbstractMit dem zunehmenden Einsatz von Holz für Ingenieurbauwerke steigen die Ansprüche an eine montagefreundliche und materialgerechte Ausbildung effektiver Anschlüsse mit hoher Tragfähigkeit auch unter mehrachsig interagierenden Beanspruchungen. Dieser Beitrag stellt baustellengerechte Varianten für Zug‐, Druck‐ sowie Biegeanschlüsse im Holzbau auf der Basis polymergebundener Vergussmassen vor. Hierbei werden typisierte frei geformte Einbauteile, z. B. aus Stahl mit metrischem Gewinde als Muffen‐ oder Gewindeanschluss, bereits vom Hersteller mittels „Vergusskleben“ in nahezu beliebig geformten, auch größer dimensionierten Ausnehmungen im Holzbauteil verankert. Damit ermöglichen derartige Vergusslösungen dem Holzbau nicht nur einen optimalen Kraftschluss, sondern auch das effiziente direkte Zusammenspiel mit typisierten Anschlüssen anderer Bauweisen, wie sie z. B. im Stahl‐ oder Stahlbetonbau üblich sind. In diesem Kontext können daher die als Stütze oder Biegeträger optimierten Holzbauteile effektiver als bisher eingesetzt werden. Darüber hinaus eignet sich der Polymerverguss hervorragend für die Ein‐ sowie Durchleitung lokaler hoher Druckbeanspruchungen quer zur Holzfaserrichtung. Der vorliegende Artikel zeigt zudem, dass mittels geeigneter numerischer 3‐D‐FE‐Modelle der vorhandene komplexe Beanspruchungszustand dieser Vergussanschlüsse zuverlässig beurteilt werden kann.
Sorbus aucuparia and Sorbus aria as a Source of Antioxidant Phenolics, Tocopherols, and Pigments
Authors: Šavikin Katarina P. , Zdunić Gordana M. , Krstić‐Milošević Dijana B. , Šircelj Helena J. , Stešević Danijela D. , Pljevljakušić Dejan S. 
Published: August 2017

Due to its nutritive and medicinal properties, berries of some Sorbus species are used for the preparation of jams and jelly as well as in traditional medicine. On the other hand, their chemical composition is not much studied especially of those grown in Balkan Peninsula. We have analyzed individual phenolics, tocopherols, carotenoids and chlorophylls using HPLC in berries from Sorbus aucuparia and Sorbus aria collected in different localities in Serbia and Montenegro together with the amounts of total phenolics and proanthocyanidins as well as their radical scavenging activity against DPPH radical. Berries of S. aucuparia were richer source of polyphenolics in comparision with S. aria and, regardless the species and locality, caffeoylquinic acids such as neochlorogenic and chlorogenic acid were the most abundant compounds. Among analyzed tocopherols the most abundant in all samples was α‐tocopherol (0.48 – 19.85 μg/g dw) as it was β‐carotene among carotenoids (mean concentration of 0.98 μg/g dw in S. aucuparia and 0.40 μg/g dw in S. aria, respectively). Correlation between total phenolics and DPPH radical scavenging activity was noticed. Our study represents comprehensive report on chemical composition of S. aucuparia and S. aria which could contribute to a better understanding of their quality.
Efficient Biocatalytic Reductive Aminations by Extending the Imine Reductase Toolbox
Authors: Roiban Gheorghe‐Doru , Kern Marcelo , Liu Zhi , Hyslop Julia , Tey Pei Lyn , Levine Matthew S. , Jordan Lydia S. , Brown Kristin K. , Hadi Timin , Ihnken Leigh Anne F. , Brown Murray J. B. 
Published: August 2017

AbstractChiral secondary and tertiary amines are ubiquitous in pharmaceutical, fine, and specialty chemicals, but their synthesis typically suffers from significant sustainability and selectivity challenges. Biocatalytic alternatives, such as enzyme‐catalyzed reductive amination, offer several advantages over traditional chemistry, but industrial applicability has not yet been demonstrated. Herein, we report the use of cell lysates expressing imine reductases operating at 1:1 stoichiometry for a variety of amines and carbonyls. A collection of biocatalysts with diversity in coverage of small molecules and direct industrial applicability is presented.
Reaction Engineering for Continuous Production of Silver Nanoparticles
Authors: Deshpande Javdeep B. , Kulkarni Amol A. 
Published: August 2017

AbstractA scalable process for the production of silver nanoparticles that allows for complete conversion of the limiting reactant is analyzed in detail. The kinetics of silver nanoparticle synthesis using citrate reduction are investigated and used for development of a reaction engineering model to facilitate the reactor design. The effect of temperature, pH, concentration and mixing (axial dispersion) on the rates of nucleation and growth are analyzed quantitatively. An approach that considers reaction kinetics coupled with quality of dispersion is developed for reactor design as well as selection of reactor configurations for the synthesis of specific particle sizes. The developed approach has been applied for continuous production of 10‐L suspension silver nanoparticles with very narrow particle size distribution.
Ligand Noninnocence in Iron Corroles: Insights from Optical and X‐ray Absorption Spectroscopies and Electrochemical Redox Potentials
Authors: Ganguly Sumit , Giles Logan J. , Thomas Kolle E. , Sarangi Ritimukta , Ghosh Abhik 
Published: August 2017

AbstractTwo new series of iron meso‐tris(para‐X‐phenyl)corrole (TpXPC) complexes, Fe[TpXPC]Ph and Fe[TpXPC]Tol, in which X=CF3, H, Me, and OMe, and Tol=p‐methylphenyl (p‐tolyl), have been synthesized, allowing a multitechnique electronic–structural comparison with the corresponding FeCl, FeNO, and Fe2(μ‐O) TpXPC derivatives. Optical spectroscopy revealed that the Soret maxima of the FePh and FeTol series are insensitive to the phenyl para substituent, consistent with the presumed innocence of the corrole ligand in these compounds. Accordingly, we may be increasingly confident in the ability of the substituent effect criterion to serve as a probe of corrole noninnocence. Furthermore, four complexes—Fe[TPC]Cl, Fe[TPC](NO), {Fe[TPC]}2O, and Fe[TPC]Ph—were selected for a detailed XANES investigation of the question of ligand noninnocence. The intensity‐weighted average energy (IWAE) positions were found to exhibit rather modest variations (0.8 eV over the series of corroles). The integrated Fe‐K pre‐edge intensities, on the other hand, vary considerably, with a 2.5 fold increase for Fe[TPC]Ph relative to Fe[TPC]Cl and Fe[TPC](NO). Given the approximately C4v local symmetry of the Fe in all the complexes, the large increase in intensity for Fe[TPC]Ph may be attributed to a higher number of 3d holes, consistent with an expected FeIV‐like description, in contrast to Fe[TPC]Cl and Fe[TPC](NO), in which the Fe is thought to be FeIII‐like. These results afford strong validation of XANES as a probe of ligand noninnocence in metallocorroles. Electrochemical redox potentials, on the other hand, were found not to afford a simple probe of ligand noninnocence in Fe corroles.
Catalytic Asymmetric Formal [3+2] Cycloaddition of 2‐Isocyanatomalonate Esters and Unsaturated Imines: Synthesis of Highly Substituted Chiral γ‐Lactams
Authors: Espinosa Miguel , Blay Gonzalo , Cardona Luz , Muñoz M. Carmen , Pedro José R. 
Published: August 2017

AbstractUnlike their isocyano and isothiocyanato analogues, isocyanato esters remain almost unexplored as formal 1,3‐dipoles in asymmetric catalytic reactions. The first asymmetric formal [3+2] cycloaddition involving isocyanato esters and electrophilic alkenes is reported. Diisopropyl 2‐isocyanatomalonate reacts with α,β‐unsaturated N‐(o‐anisidyl) imines in the presence of a Mg(OTf)2–BOX complex to give highly substituted chiral pyrrolidinones featuring a conjugate exocyclic double bond with excellent yields and enantiomeric excesses up to 99 %. Several transformations of the resulting heterocycles, including the synthesis of a pyroglutamic acid derivative, have been carried out.
Synergistic Effects in PtII–Porphyrinoid Dyes as Candidates for a Dual‐Action Anticancer Therapy: A Theoretical Exploration
Authors: Alberto Marta Erminia , Adamo Carlo 
Published: August 2017

AbstractThe combination of a photosensitizer (PS) with a cisplatin‐like unit represents a challenging strategy to increase the effectiveness of photodynamic therapy and to afford a dual‐action anticancer treatment. Recently, new tetra‐PtII–porphyrin conjugates have been proposed as promising multitarget agents. To reveal the effect of the PtII center on the chemical and physical properties of the PS and to explore the effect of the PS on the activation mechanism of PtII ligand before reaching its biological target, we carried out a first‐principle investigation on these tetra‐PtII–porphyrin conjugates. To propose a further advance in this novel field and to gain useful insights for the design of new, more efficient PtII–PS conjugates, we introduced structural modifications into the porphyrin dye, which involved the synthesis of the tetra‐PtII–chlorin and tetra‐PtII–bacteriochlorin derivatives. Results showed that the designed dyes better met the criteria to be successful in a dual‐action therapy, as they displayed improved optical properties and reduced the hydrolysis rate of the PtII moiety, the latter being a desirable feature to avoid many side reactions of the conjugate during their transport to the biological target.