bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect on citation inequality of differences in citation practices at the web of science subject category level
Authors: Crespo Juan A. , Herranz Neus , Li Yunrong , Ruiz‐Castillo Javier
Published: February 2014

This article studies the impact of differences in citation practices at the subfield, or Web of Science subject category level, using the model introduced in Crespo, Li, and Ruiz‐Castillo (2013a), according to which the number of citations received by an article depends on its underlying scientific influence and the field to which it belongs. We use the same Thomson Reuters data set of about 4.4 million articles used in Crespo et al. (2013a) to analyze 22 broad fields. The main results are the following: First, when the classification system goes from 22 fields to 219 subfields the effect on citation inequality of differences in citation practices increases from ∼14% at the field level to 18% at the subfield level. Second, we estimate a set of exchange rates (ERs) over a wide [660, 978] citation quantile interval to express the citation counts of articles into the equivalent counts in the all‐sciences case. In the fractional case, for example, we find that in 187 of 219 subfields the ERs are reliable in the sense that the coefficient of variation is smaller than or equal to 0.10. Third, in the fractional case the normalization of the raw data using the ERs (or subfield mean citations) as normalization factors reduces the importance of the differences in citation practices from 18% to 3.8% (3.4%) of overall citation inequality. Fourth, the results in the fractional case are essentially replicated when we adopt a multiplicative approach.
Beyond bag‐of‐words: Bigram‐enhanced context‐dependent term weights
Authors: Dang Edward K. F. , Luk Robert W. P. , Allan James
Published: February 2014

While term independence is a widely held assumption in most of the established information retrieval approaches, it is clearly not true and various works in the past have investigated a relaxation of the assumption. One approach is to use n‐grams in document representation instead of unigrams. However, the majority of early works on n‐grams obtained only modest performance improvement. On the other hand, the use of information based on supporting terms or “contexts” of queries has been found to be promising. In particular, recent studies showed that using new context‐dependent term weights improved the performance of relevance feedback (RF) retrieval compared with using traditional bag‐of‐words BM25 term weights. Calculation of the new term weights requires an estimation of the local probability of relevance of each query term occurrence. In previous studies, the estimation of this probability was based on unigrams that occur in the neighborhood of a query term. We explore an integration of the n‐gram and context approaches by computing context‐dependent term weights based on a mixture of unigrams and bigrams. Extensive experiments are performed using the title queries of the Text Retrieval Conference (TREC)‐6, TREC‐7, TREC‐8, and TREC‐2005 collections, for RF with relevance judgment of either the top 10 or top 20 documents of an initial retrieval. We identify some crucial elements needed in the use of bigrams in our methods, such as proper inverse document frequency (IDF) weighting of the bigrams and noise reduction by pruning bigrams with large document frequency values. We show that enhancing context‐dependent term weights with bigrams is effective in further improving retrieval performance.
The Application of CdSe Quantum Dots with Multicolor Emission as Fluorescent Probes for Cell Labeling
Authors: Zhao Mei‐Xia , Li Yang , Zeng Er‐Zao , Wang Chao‐Jie
Published: February 2014

Herein, highly luminescent CdSe quantum dots (QDs) with emissions from the blue to the red region of visible light were synthesized by using a simple method. The emission range of the CdSe QDs could be tuned from λ=503 to 606 nm by controlling the size of the CdSe QDs. Two amino acids, L‐tryptophan (L‐Trp) and L‐arginine (L‐Arg), were used as coating agents. The quantum yield (QY) of CdSe QDs (green color) with an optimized thickness could reach up to 52 %. The structures and compositions of QDs were examined by using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Optical properties were studied by using UV/Vis and photoluminescence (PL) spectroscopy and a comparison was made between uncoated and coated CdSe QDs. The amino acid‐modified β‐cyclodextrin (CD)‐coated CdSe QDs presented lower cytotoxicity to cells for 48 h. Furthermore, amino acid‐modified β‐CD‐coated green CdSe QDs in HepG2 cells were assessed by using confocal laser scanning fluorescence microscopy. The results showed that amino acid‐modified β‐CD‐coated green CdSe QDs could enter tumor cells efficiently and indicated that biomolecule‐coated QDs could be used as a potential fluorescent probe.
Stochastic Networked Control Systems with Dynamic Protocols
Authors: Antunes Duarte , Hespanha João P. , Silvestre Carlos
Published: February 2014

We consider networked control systems in which sensors, controllers, and actuators communicate through a shared network that introduces stochastic intervals between transmissions, delays, and packet drops. Access to the communication medium is mediated by a protocol that determines which node (one of the sensors, one of the actuators, or the controller) is allowed to transmit a message at each sampling/actuator‐update time. We provide conditions for mean exponential stability of the networked closed loop in terms of matrix inequalities, both for investigating the stability of given protocols, such as static round‐robin protocols and dynamic maximum error first‐try once discard protocols, and conditions to design new dynamic protocols. The main result entailed by these conditions is that, if the networked closed loop is stable for a static protocol, then we can provide a dynamic protocol for which the networked closed loop is also stable. The stability conditions also allow for obtaining an observer‐protocol pair that reconstructs the state of a linear time invariant plant in a mean exponential sense and for less conservative stability results than other conditions previously appearing in the literature.
Understanding and attributing the Euro‐Russian summer blocking signatures
Authors: Ruti Paolo M. , Dell'Aquila A. , Giorgi F.
Published: February 2014

In this work, we focus on summer blocking events over the Euro‐Russian region related with heat waves. An analysis of the main characteristics of summer Euro‐Russian blocking events in global Reanalysis as well as in the 20th century CLIVAR atmospheric simulations is carried out to assess whether anthropogenic forcing might have affected the blocking events occurrence and the associated heat waves strength in recent decades. Over the Euro‐Russian region, blocking episodes, associated to warm events over Northern and Central Europe, become significantly longer in the second half of the century when the anthropogenic forcing is included in the simulations.
Zum Potenzial von Kohlenstofffaserverbundwerkstoffen in Bauanwendungen
Authors: Schmohl Andreas , Adamow Katharina , Martens Nadine , Breuer Klaus
Published: February 2014

Der Beitrag diskutiert die Anwendung von Kohlenstofffaserverbundwerkstoffen im Bauwesen. Es wird aufgezeigt, dass Kohlenstofffaserverbundwerkstoffe in bestimmten Bauanwendungen bereits etabliert sind, z. B. zur Verstärkung der Statik von Gebäuden und Brücken sowie als Konstruktionswerkstoff. Andererseits sollen spezielle Potenziale des Materials jenseits der mechanischen Eigenschaften identifiziert werden, die sich für Anwendungen im Bauwesen ableiten lassen. Ausgewählte Anwendungsbeispiele, die sich auf vier charakteristischen Eigenschaften des Materials bzw. des Fertigungsprozesses zurückführen lassen, werden beschrieben: 1) Nutzung der Anisotropie zur Konstruktion flexibler und zugleich steifer Bauteile, 2) Integration von (Multi‐)Funktionalitäten, 3) Nutzung des geringen Wärmeausdehnungskoeffizienten und 4) Einsatz von recyclierten Kohlenstofffasern in anorganischer Matrix.

Potential of carbon fibre composites in civil engineering applications. The paper discusses the application of carbon fibre composite materials in the building industry. It shows that carbon fibre composites are already established in certain areas of civil engineering, e.g. for the strengthening of the statics of buildings and bridges and as construction material. On the other hand special potential of the material, apart from mechanical features, which are advantageous in construction engineering, are identified. Selected examples of specific applications deduced from four characteristic properties of the material and the manufacturing process respectively, are described: 1) Utilisation of the anisotropy for the construction of flexible and at the same time stiff construction components, 2) integration of (multi‐)functionalities, 3) utilisation of the low thermal expansion coefficient and 4) application of recycled carbon fibres in inorganic matrices.
APPLIED BEHAVIOR ANALYSIS IN ACQUIRED BRAIN INJURY REHABILITATION: A META‐ANALYSIS OF SINGLE‐CASE DESIGN INTERVENTION RESEARCH
Authors: Heinicke Megan R. , Carr James E.
Published: February 2014

The purpose of this meta‐analysis was to complete a systematic evidence‐based review of published behavioral treatment studies employing single‐case designs with both children and adults with acquired brain injury. Peer‐reviewed journals were searched using PsycINFO, Medline, and ERIC databases with combinations of terms such as brain injury, behavior disorder, behavior therapy, behavior modification, behavior analysis, and verbal behavior. A total of 112 acquisition and reduction studies met the established inclusion criteria. The data extracted from each study included specific details about the participants, target responses, intervention characteristics, use of functional assessment, and outcome characteristics. A data extraction software program was also used to extract data from graphs to calculate percentage of nonoverlapping data as an effect size. The studies were then evaluated along several dimensions from multiple evidence‐based practice frameworks. Collectively, interventions targeted a wide range of behaviors for acquisition and reduction, but only five interventions were classified as well established according to the American Psychological Association Division 12 criteria. Furthermore, methodology of the identified studies was found to be relatively poor. A variety of methodological concerns are discussed. Copyright © 2014 John Wiley & Sons, Ltd.
An undergraduate study of two transcription factors that promote lateral root formation
Authors: Bargmann Bastiaan O. R. , Birnbaum Kenneth D. , Brenner Eric D.
Published: February 2014

We present a lab that enables students to test the role of genes involved in the regulation of lateral roots growth in the model plant Arabidopsis thaliana. Here, students design an experiment that follows the effects of the hormone auxin on the stimulation of genes involved in the formation of lateral root initials. These genes, known as lateral organ boundary domain containing protein (LBD) genes, are upregulated in the presence of auxin as part of a multistep molecular and biochemically controlled pathway. Depending on which LBD gene is tested, and the stage of root development, expression patterns are localized in a discrete and punctate fashion at the site of lateral root initials (LBD33), or reveal a broader localization pattern (LBD16). Students view expression using the reporter gene GUS (beta‐glucuronidase). Before GUS staining, students view root growth in a “pseudo‐aseptic” agar‐based environment that allows complete visualization of whole root development to determine the proper stage to test molecular expression. © 2014 by The International Union of Biochemistry and Molecular Biology, 42(3):XXXXX–XXXXX, 2014.
Fast separation of native proteins using sub‐2 µm nonporous silica particles in a chromatographic cake
Authors: Niu Ruijuan , Min Yi , Geng Xindu
Published: February 2014

A novel method for the fast separation of native proteins was investigated using sub‐2 µm nonporous silica packing inside a chromatographic cake having a diameter much larger than its thickness. Various silica‐based particles ranging from 630 nm to 1.2 µm were synthesized and chemically modified with polyethylene glycol 600. The packing material was laterally packed into a series of chromatographic cakes containing the same diameter (10 mm) and different thicknesses, ranging from 2 to 10 mm, and tested by hydrophobic interaction chromatography. The results showed that the sub‐2 µm NPS particles in a small chromatographic cake were found to have a high efficiency at a flow rate of 10 mL/min and a backpressure of <20 MPa. The effect of the thickness of the chromatographic cake on the resolution of the proteins was also investigated and it was found that too short a column length could dramatically decrease the protein resolution; the minimum column length was also qualitatively evaluated. The presented method is expected to be useful for routine analysis of native and/or intact proteins in hospitals and as a tool for the fast screening protein drugs and optimization of experimental laboratory conditions. Copyright © 2014 John Wiley & Sons, Ltd.
Effect of realgar on extracellular amino acid neurotransmitters in hippocampal CA1 region determined by online microdialysis–dansyl chloride derivatization–high‐performance liquid chromatography and fluorescence detection
Authors: Huo Taoguang , Zhang Yinghua , Li Weikai , Yang Huilei , Jiang Hong , Sun Guifan
Published: February 2014

An online microdialysis (MD)–dansyl chloride (Dns) derivatization–high‐performance liquid chromatography (HPLC) and fluorescence detection (FD) system was developed for simultaneous determination of eight extracellular amino acid neurotransmitters in hippocampus. The MD probe was implanted in hippocampal CA1 region. Dialysate and Dns were online mixed and derivatized. The derivatives were separated on an ODS column and detected by FD. The developed online system showed good linearity, precision, accuracy and recovery. This online MD‐HPLC system was applied to monitor amino acid neurotransmitters levels in rats exposed to realgar (0.3, 0.9 and 2.7 g/kg body weight). The result shows that glutamate concentrations were significantly increased (p < 0.05) in hippocampal CA1 region of rats exposed to three doses of realgar. A decrease in γ‐aminobutyric acid concentrations was found in rats exposed to medium and high doses of realgar (p < 0.05). Elevation of excitotoxic index (EI) values in hippocampal CA1 region of realgar‐exposed rats was observed (p < 0.05). Positive correlation was found between EI values and arsenic contents in hippocampus of realgar‐exposed rats, which indicates that the change in extracellular EI values is associated with arsenic accumulation in hippocampus. The developed online MD–Dns derivatization–HPLC–FD system provides a new experimental method for studying the effect of toxic Chinese medicines on amino acid neurotransmitters. Copyright © 2014 John Wiley & Sons, Ltd.
Simultaneous determination of cotinine and trans‐3‐hydroxycotinine in urine by automated solid‐phase extraction using gas chromatography–mass spectrometry
Authors: Chiadmi Fouad , Schlatter Joël
Published: February 2014

A gas chromatography–mass spectrometry method was developed and validated for the simultaneous automated solid‐phase extraction and quantification of cotinine and trans‐3‐hydroxycotinine in human urine. Good linearity was observed over the concentration ranges studied (R2 > 0.99). The limit of quantification was 10 ng/mL for both analytes. The limits of detection were 0.06 ng/mL for cotinine (COT) and 0.02 ng/mL for trans‐3‐hydroxycotinine (OH‐COT). Accuracy for COT ranged from 0.98 to 5.28% and the precision ranged from 1.24 to 8.78%. Accuracy for OH‐COT ranged from −2.66 to 3.72% and the precision ranged from 3.15 to 7.07%. Mean recoveries for cotinine and trans‐3‐hydroxycotinine ranged from 77.7 to 89.1%, and from 75.4 to 90.2%, respectively. This analytical method for the simultaneous measurement of cotinine and trans‐3‐hydroxycotinine in urine will be used to monitor tobacco smoking in pregnant women and will permit the usefulness of trans‐3‐hydroxycotinine as a specific biomarker of tobacco exposure to be determined. © 2014 The Authors. Biomedical Chromatography published by John Wiley & Sons Ltd.
Advanced near‐infrared monitor for stable real‐time measurement and control of Pichia pastoris bioprocesses
Authors: Goldfeld Marina , Christensen Jens , Pollard David , Gibson Elizabeth R. , Olesberg Jonathon T. , Koerperick Edwin J. , Lanz Kaylee , Small Gary W. , Arnold Mark A. , Evans Christine E.
Published: February 2014

Near‐infrared spectroscopy is considered to be one of the most promising spectroscopic techniques for upstream bioprocess monitoring and control. Traditionally the nature of near‐infrared spectroscopy has demanded multivariate calibration models to relate spectral variance to analyte concentrations. The resulting analytical measurements have proven unreliable for the measurement of metabolic substrates for bioprocess batches performed outside the calibration process. This paper presents results of an innovative near‐infrared spectroscopic monitor designed to follow the concentrations of glycerol and methanol, as well as biomass, in real time and continuously during the production of a monoclonal antibody by a Pichia pastoris high cell density process. A solid state instrumental design overcomes the ruggedness limitations of conventional interferometer‐based spectrometers. Accurate monitoring of glycerol, methanol, and biomass is demonstrated over 274 days postcalibration. In addition, the first example of feedback control to maintain constant methanol concentrations, as low as 1 g/L, is presented. Postcalibration measurements over a 9‐month period illustrate a level of reliability and robustness that promises its adoption for online bioprocess monitoring throughout product development, from early laboratory research and development to pilot and manufacturing scale operation. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:749–759, 2014
The Fairness of National Decision‐making Procedures: The Views of Adolescents in 18 European Countries
Authors: Ellenbroek Moniek , Verkuyten Maykel , Thijs Jochem , Poppe Edwin
Published: February 2014

This study examines adolescents' evaluation of the fairness of three forms of democratic decision‐making procedures (direct democracy, representative democracy and group representation) and one non‐democratic procedure (oligarchy). Social dominance orientation‐Egalitarianism (SDO‐E), religious group identification and the countries' level of democracy are examined as predictors. The 2008 Europroject dataset was used, which contained 4441 native majority adolescents (mean age = 16.1 years) in 18 European countries. Adolescents evaluated direct democracy as most fair, followed by group representation, representative democracy and oligarchy. This rank order was found independent of the issue under consideration (moral or social), and of SDO‐E and religious identification, and across the countries. In addition, adolescents scoring higher on SDO‐E and on religious identification found group representation and non‐democratic oligarchy fairer. Copyright © 2014 John Wiley & Sons, Ltd.
Macromolecular Uptake of Alkyl‐Chain‐Modified Guanidinoglycoside Molecular Transporters
Authors: Inoue Makoto , Wexselblatt Ezequiel , Esko Jeffrey D. , Tor Yitzhak
Published: February 2014

Guanidinoglycosides, a family of cellular transporters capable of delivering high Mw biopolymers, have previously been shown to display high selectivity for cell‐surface heparan sulfate proteoglycans and promote their clustering. Herein, the internalization mechanism of amphiphilic guanidinoglycoside derivatives was investigated by cell‐surface FRET analysis. Unexpectedly, although the heparan sulfate selectivity is maintained, the cellular uptake of these derivatives does not appear to involve clustering of the proteoglycans on the cell surface. This suggests a distinct uptake mechanism when compared to the parent guanidinoglycoside‐based carriers.
Biofragments: An Approach towards Predicting Protein Function Using Biologically Related Fragments and its Application to Mycobacterium tuberculosis CYP126
Authors: Hudson Sean A. , Mashalidis Ellene H. , Bender Andreas , McLean Kirsty J. , Munro Andrew W. , Abell Chris
Published: February 2014

We present a novel fragment‐based approach that tackles some of the challenges for chemical biology of predicting protein function. The general approach, which we have termed biofragments, comprises two key stages. First, a biologically relevant fragment library (biofragment library) can be designed and constructed from known sets of substrate‐like ligands for a protein class of interest. Second, the library can be screened for binding to a novel putative ligand‐binding protein from the same or similar class, and the characterization of hits provides insight into the basis of ligand recognition, selectivity, and function at the substrate level. As a proof‐of‐concept, we applied the biofragments approach to the functionally uncharacterized Mycobacterium tuberculosis (Mtb) cytochrome P450 isoform, CYP126. This led to the development of a tailored CYP biofragment library with notable 3D characteristics and a significantly higher screening hit rate (14 %) than standard drug‐like fragment libraries screened previously against Mtb CYP121 and 125 (4 % and 1 %, respectively). Biofragment hits were identified that make both substrate‐like type‐I and inhibitor‐like type‐II interactions with CYP126. A chemical‐fingerprint‐based substrate model was built from the hits and used to search a virtual TB metabolome, which led to the discovery that CYP126 has a strong preference for the recognition of aromatics and substrate‐like type‐I binding of chlorophenol moieties within the active site near the heme. Future catalytic analyses will be focused on assessing CYP126 for potential substrate oxidative dehalogenation.
A Simple Strategy for Glycosyltransferase‐Catalyzed Aminosugar Nucleotide Synthesis
Authors: Zhang Jianjun , Singh Shanteri , Hughes Ryan R. , Zhou Maoquan , Sunkara Manjula , Morris Andrew J. , Thorson Jon S.
Published: February 2014

A set of 2‐chloro‐4‐nitrophenyl glucosamino‐/xylosaminosides were synthesized and assessed as potential substrates in the context of glycosyltransferase‐catalyzed formation of the corresponding UDP/TDP‐α‐D‐glucosamino‐/xylosaminosugars and in single‐vessel model transglycosylation reactions. This study highlights a robust platform for aminosugar nucleotide synthesis and reveals OleD Loki to be a proficient catalyst for U/TDP‐aminosugar synthesis and utilization.
Transfer Hydrogenation of Cellulose‐based Oligomers over Carbon‐supported Ruthenium Catalyst in a Fixed‐bed Reactor
Authors: Shrotri Abhijit , Kobayashi Hirokazu , Tanksale Akshat , Fukuoka Atsushi , Beltramini Jorge
Published: February 2014

Ru supported on activated carbon was found to be active for the transfer hydrogenation of cellulose oligomers, which were produced by the milling of acidulated microcrystalline cellulose. A C6 sugar alcohol yield of 85 % was obtained in less than 1 h reaction time in a batch reactor. Optimum reaction conditions for transfer hydrogenation were determined as 180 °C and a pH above 2.2 using glucose as a substrate. Use of deuterium as a marker established that direct transfer of hydride species from 2‐propanol to glucose occurs through the dihydride mechanism. Formation of molecular hydrogen from 2‐propanol dehydrogenation was found to be a side reaction, with little influence on the glucose hydrogenation step. Conversion of cellulose oligomers to hexitols was also achieved in a continuous flow fixed‐bed reactor with 36.4 % yield at a liquid hourly space velocity of 4.7 h−1. The catalytic activity did not decrease even after 12 h of the onstream reaction.
Redox‐Induced Spin‐State Switching and Mixed Valency in Quinonoid‐Bridged Dicobalt Complexes
Authors: Schweinfurth David , Rechkemmer Yvonne , Hohloch Stephan , Deibel Naina , Peremykin Irina , Fiedler Jan , Marx Raphael , Neugebauer Petr , van Slageren Joris , Sarkar Biprajit
Published: February 2014

The complexes [{(tmpa)CoII}2(μ‐L1)2−]2+ (12+) and [{(tmpa)CoII}2(μ‐L2)2−]2+ (22+), with tmpa=tris(2‐pyridylmethyl)amine, H2L1=2,5‐di‐[2‐(methoxy)‐anilino]‐1,4‐benzoquinone, and H2L2=2,5‐di‐[2‐(trifluoromethyl)‐anilino]‐1,4‐benzoquinone, were synthesized and characterized. Structural analysis of 22+ revealed a distorted octahedral coordination around the cobalt centers, and cobalt–ligand bond lengths that match with high‐spin CoII centers. Superconducting quantum interference device (SQUID) magnetometric studies on 12+ and 22+ are consistent with the presence of two weakly exchange‐coupled high‐spin cobalt(II) ions, for which the nature of the coupling appears to depend on the substituents on the bridging ligand, being antiferromagnetic for 12+ and ferromagnetic for 22+. Both complexes exhibit several one‐electron redox steps, and these were investigated with cyclic voltammetry and UV/Vis/near‐IR spectroelectrochemistry. For 12+, it was possible to chemically isolate the pure forms of both the one‐electron oxidized mixed‐valent 13+ and the two‐electron oxidized isovalent 14+ forms, and characterize them structurally as well as magnetically. This series thus provided an opportunity to investigate the effect of reversible electron transfers on the total spin‐state of the molecule. In contrast to 22+, for 14+ the metal–ligand distances and the distances within the quinonoid ligand point to the existence of two low‐spin CoIII centers, thus showing the innocence of the quintessential non‐innocent ligands L. Magnetic data corroborate these observations by showing the decrease of the magnetic moment by roughly half (neglecting spin exchange effects) on oxidizing the molecules with one electron, and the disappearance of a paramagnetic response upon two‐electron oxidation, which confirms the change in spin state associated with the electron‐transfer steps.
PdII‐Catalyzed Mild CH ortho Arylation and Intramolecular Amination Oriented by a Phosphinamide Group
Authors: Guan Jing , Wu Guo‐Jie , Han Fu‐She
Published: February 2014

A novel protocol for the Pd‐catalyzed ortho‐arylation of aryl phosphinamide with boronic acid is reported. By using phosphinamide as a new directing group, the reaction proceeds efficiently under mild conditions at 40 °C. Mechanistic studies reveal that the reaction proceeds via a PdII to Pd0 cycle. The phosphinamide group is also shown to be an effective orienting group for direct CH amination.
Displacement Plating of a Mesoporous Pt Skin onto Co Nanochains in a Low‐Concentration Surfactant Solution
Authors: Li Cuiling , Imura Masataka , Yamauchi Yusuke
Published: February 2014

Mesoporous Pt skins on Co nanochains are successfully synthesized by a displacement reaction between Pt species and a Co support with the assistance of surfactant micelles. The assembly of surfactant micelles on Co nanochains plays a key role in the formation of mesoporous Pt layers. The evolution of the mesoporous Pt layers is carefully studied at different time intervals. As the reaction time increases, the mesoporous Pt layers become thicker, and well‐defined mesoporous structures gradually develop. The obtained mesoporous Pt skin exhibits high activity and superior CO tolerance in the electro‐oxidation reaction of methanol. The mesoporous Pt skin also shows very high durability, and only a 20.2 % loss of the Pt electrochemical surface area is found even after a harsh durability test.
Electrochemical Preparation of N‐Doped Cobalt Oxide Nanoparticles with High Electrocatalytic Activity for the Oxygen‐Reduction Reaction
Authors: Yu Hongtao , Li Yunchao , Li Xiaohong , Fan Louzhen , Yang Shihe
Published: February 2014

Nitrogen‐doped CoO (N‐CoO) nanoparticles with high electrocatalytic activity for the oxygen‐reduction reaction (ORR) were fabricated by electrochemical reduction of CoCl2 in acetonitrile solution at cathodic potentials. The initially generated, highly reactive nitrogen‐doped Co nanoparticles were readily oxidized to N‐CoO nanoparticles in air. In contrast to their N‐free counterparts (CoO or Co3O4), N‐CoO nanoparticles with a N content of about 4.6 % exhibit remarkable ORR electrocatalytic activity, stability, and immunity to methanol crossover in an alkaline medium. The CoNx active sites in the CoO nanoparticles are held responsible for the high ORR activity. This work opens a new path for the preparation of nitrogen‐doped transition metal oxide nanomaterials, which are promising electrocatalysts for fuel cells.
Metal‐to‐Ligand Alkyl Migration Inducing Carbon–Sulfur Bond Cleavage in Dialkyl Yttrium Complexes Supported by Thiazole‐Containing Amidopyridinate Ligands: Synthesis, Characterization, and Catalytic Activity in the Intramolecular Hydroamination Reaction
Authors: Lyubov Dmitry M. , Luconi Lapo , Rossin Andrea , Tuci Giulia , Cherkasov Anton V. , Fukin Georgy K. , Giambastiani Giuliano , Trifonov Alexander A.
Published: February 2014

Neutral YIII dialkyl complexes supported by tridentate N−,N,N monoanionic methylthiazole– or benzothiazole–amidopyridinate ligands have been prepared and completely characterized. Studies on their stability in solution revealed progressive rearrangement of the coordination sphere in the benzothiazole‐containing system through an unprecedented metal‐to‐ligand alkyl migration and subsequent thiazole ring opening. Attempts to synthesize hydrido species from the dialkyl precursor led to the generation of a dimeric yttrium species stabilized by a trianionic N−,N,N−,S− ligand as the result of metal‐to‐ligand hydride migration with chemoselective thiazole ring opening and subsequent dimerization through intermolecular addition of the residual YH group to the imino fragment of a second equivalent of the ring‐opened intermediate. DFT calculations were used to elucidate the thermodynamics and kinetics of the process, in support of the experimental evidence. Finally, all isolated yttrium complexes, especially their cationic forms prepared by activation with the Lewis acid Ph3C+[B(C6F5)4]−, were found to be good candidate catalysts for intramolecular hydroamination/cyclization reactions. Their catalytic performance with a number of primary and secondary amino alkenes was assessed.
Ene‐ene‐yne Reactions: Activation Strain Analysis and the Role of Aromaticity
Authors: Fernández Israel , Bickelhaupt F. Matthias , Cossío Fernando P.
Published: February 2014

The trend in reactivity of the thermal cycloisomerization reactions of 1,3‐hexadien‐5‐ynes, ABCDEF, were explored and analyzed by using density functional theory at the M06‐2X/def2‐TZVPP level. These reactions proceed through formally aromatic transition states to form a bent‐allene intermediate with relatively high activation barriers. Activation‐strain analyses show that the major factor controlling this Hopf cyclization is the geometrical strain energy associated with the rotation of the terminal [A] group. This rotation is necessary for achieving a favorable HOMO–LUMO overlap with the yne‐moiety [F] associated with the formation of the new AF single bond. In addition, the relationship between the aromaticity of the corresponding cyclic transition states (all six‐membered rings) and the computed activation barriers were analyzed. The calculations also indicate that the aromatization of the bent‐allene structures takes place through two consecutive 1,2‐hydrogen shifts, the second one exhibiting negligible energy barriers.
Synthesis of Oxacyclic Scaffolds via Dual Ruthenium Hydride/Brønsted Acid‐Catalyzed Isomerization/Cyclization of Allylic Ethers
Authors: Ascic Erhad , Ohm Ragnhild G. , Petersen Rico , Hansen Mette R. , Hansen Casper L. , Madsen Daniel , Tanner David , Nielsen Thomas E.
Published: February 2014

A ruthenium hydride/Brønsted acid‐catalyzed tandem sequence is reported for the synthesis of 1,3,4,9‐tetrahydropyrano[3,4‐b]indoles (THPIs) and related oxacyclic scaffolds. The process was designed on the premise that readily available allylic ethers would undergo sequential isomerization, first to enol ethers (Ru catalysis), then to oxocarbenium ions (Brønsted acid catalysis) amenable to endo cyclization with tethered nucleophiles. This methodology provides not only an attractive alternative to the traditional oxa‐Pictet–Spengler reaction for the synthesis of THPIs, but also convenient access to THPI congeners and other important oxacycles such as acetals.
The Significant Role of Carboxylated Carbonaceous Fragments in the Electrochemistry of Carbon Nanotubes
Authors: Ma Xiao , Jia Li , Zhang Lu , Zhu Liande
Published: February 2014

Carbon nanotubes (CNTs) have been widely employed as electrode materials in diverse branches of electrochemistry, which are claimed to display dramatically improved electrochemical behaviour compared to the conventional carbon materials. But a series of recent publications have demonstrated that the electrocatalysis of CNTs might be due to the presence of some impurities, such as metallic catalysts, nanographitic particles and amorphous carbon. For this reason, CNTs are usually purified or treated with nitric acid or nitric and sulphuric acid prior to their versatile applications. However, the strong acidic and oxidative conditions are so aggressive that serious erosion of the tube structures has inevitably taken place, which creates defects on the sidewalls and gives rise to numerous molecular byproducts, commonly referred as carboxylated carbonaceous fragments (CCFs). The adsorption of CCFs on CNTs greatly alters the surface conditions of CNTs which may significantly impact on their electrochemical properties. To this end, we wish to disclose whether the electrocatalysis of the nitric acid purified CNTs is affected by the adsorption of the CCFs. Ascorbic acid (AA) and β‐nicotinamide adenine dinucleotide (NADH) as selected as the targeting benchmarks that are known to be insensitive to the presence of metallic impurities, which may guarantee the preclusion of the promoting contributions from the metallic catalysts resident in CNTs. We have demonstrated that the electrocatalytic activities of the CNTs are actually dominated by the adsorbed CCFs generated during the acidic pre‐treatment. After removal of the CCFs by base rinse, the electrocatalytic properties of CNTs are greatly deteriorated and degraded to the level similar to the conventional graphite powder. We believe this finding is particularly meaningful to uncover the mysterious electrocatalysis of CNTs.
Design of Amphiphilic Peptide Geometry towards Biomimetic Self‐Assembly of Chiral Mesoporous Silica
Authors: Huang Zhehao , Yao Yuan , Che Shunai
Published: February 2014

In nature, diatoms and sponges are exquisite examples of well‐defined structures produced by silica biomineralisation, in which proteins play an important role. However, the artificial peptide templating route for the silica mesostructure remains a formidable and unsolved challenge. Herein, we report our effort on the design of amphiphilic peptides for synthesising a highly ordered two‐dimensional (2D)‐hexagonal and lamellar chiral silica mesostructure using trimethoxysilylpropyl‐N,N,N‐trimethylammonium chloride as the co‐structure directing agent (CSDA). The geometry of the peptide was designed by adding proline residues into the hydrophobic chain of the peptide to break the β‐sheet conformation by weakening the intermolecular hydrogen bonds; this led to the mesophase transformation from the most general lamellar structure to the 2D hexagonal P6mm mesostructure by increasing the amphiphilic molecules packing parameter g. Enantiomerically pure chiral mesostructures were formed thanks to the intrinsic chirality and relatively strong intermolecular hydrogen bonds of peptides.
Light Harvesting and Amplification of Emission of Donor Perylene–Acceptor Perylene Aggregates in Aqueous Medium
Authors: Sukul Pradip K. , Datta Ayan , Malik Sudip
Published: February 2014

With the aid of rational design, we have synthesized a pair of water‐soluble donor‐ and acceptor‐type twisted perylene bisimide units, which together form aggregates upon lowering the pH of the medium, providing bright yellow fluorescence. The light‐harvesting efficiency of the co‐assembled system can be tuned by controlling the ratio of donor to acceptor and 98.1 % efficiency has been achieved.
A Novel Hybrid Metal–Organic Framework–Polymeric Monolith for Solid‐Phase Microextraction
Authors: Lin Chen‐Lan , Lirio Stephen , Chen Ya‐Ting , Lin Chia‐Her , Huang Hsi‐Ya
Published: February 2014

This study describes the fabrication of a novel hybrid metal–organic framework– organic polymer (MOF–polymer) for use as a stationary phase in fritless solid‐phase microextraction (SPME) for validating analytical methods. The MOF–polymer was prepared by using ethylene dimethacrylate (EDMA), butyl methacrylate (BMA), and an imidazolium‐based ionic liquid as porogenic solvent followed by microwave‐assisted polymerization with the addition of 25 % MOF. This novel hybrid MOF–polymer was used to extract penicillin (penicillin G, penicillin V, oxacillin, cloxacillin, nafcillin, dicloxacillin) under different conditions. Quantitative analysis of the extracted penicillin samples using the MOF–organic polymer for SPME was conducted by using capillary electrochromatography (CEC) coupled with UV analysis. The penicillin recovery was 63–96.2 % with high reproducibility, sensitivity, and reusability. The extraction time with the proposed fabricated SPME was only 34 min.
Complexes of Monocationic Group 13 Elements with Pentaphospha‐ and Pentaarsaferrocene
Authors: Fleischmann Martin , Welsch Stefan , Krauss Hannes , Schmidt Monika , Bodensteiner Michael , Peresypkina Eugenia V. , Sierka Marek , Gröger Christian , Scheer Manfred
Published: February 2014

Reactions of the sandwich complexes [Cp*Fe(η5‐E5)] (Cp*=η5‐C5Me5; E=P (1), As (2)) with the monovalent Group 13 metals Tl+, In+, and Ga+ containing the weakly coordinating anion [TEF] ([TEF]=[Al{OC(CF3)3}4]−) are described. Here, the one‐dimensional coordination polymers [M(μ,η5:η1‐E5FeCp*)3]n[TEF]n (E=P, M=Tl (3 a), In (3 b), Ga (3 c); E=As, M=Tl (4 a), In (4 b)) are obtained as sole products in good yields. All products were analyzed by single‐crystal X‐ray diffraction, revealing a similar assembly of the products with η5‐bound E5 ligands and very weak σ‐interactions between one P or As atom of the ring to the neighbored Group 13 metal cation. By exchanging the [TEF] anion of 4 a for the larger [FAl] anion ([FAl]=[FAl{OC6F10(C6F5)}3]−), the coordination compound [Tl{(η5‐As5)FeCp*}3][FAl] (5) without any σ‐interactions of the As5‐ring is obtained. All products are readily soluble in CH2Cl2 and exhibit a dynamic coordination behavior in solution, which is supported by NMR spectroscopy and ESI‐MS spectrometry as well as by osmometric molecular‐weight determination. For a better understanding of the proceeding equilibrium DFT calculations of the cationic complexes were performed for the gas phase and in solution. Furthermore, the 31P{1H} magic‐angle spinning (MAS) NMR spectra of 3 a–c are presented and the first crystal structure of the starting material 2 was determined.
Unusual Nitrile–Nitrile and Nitrile–Alkyne Coupling of FcCN and FcCCCN
Authors: Becker Lisanne , Strehler Frank , Korb Marcus , Arndt Perdita , Spannenberg Anke , Baumann Wolfgang , Lang Heinrich , Rosenthal Uwe
Published: February 2014

The reactions of the Group 4 metallocene alkyne complexes, [Cp*2M(η2‐Me3SiC2SiMe3)] (1 a: M=Ti, 1 b: M=Zr, Cp*=η5‐pentamethylcyclopentadienyl), with the ferrocenyl nitriles, FcCN and FcCCCN (Fc=Fe(η5‐C5H5)(η5‐C5H4)), is described. In case of FcCN an unusual nitrile–nitrile CC homocoupling was observed and 1‐metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes (3 a, b) were obtained. As the first step of the reaction with 1 b, the nitrile was coordinated to give [Cp*2Zr(η2‐Me3SiC2SiMe3)(NC‐Fc)] (2 b). The reactions with the 3‐ferrocenyl‐2‐propyne‐nitrile FcCCCN lead to an alkyne–nitrile CC coupling of two substrates and the formation of 1‐metalla‐2‐aza‐cyclopenta‐2,4‐dienes (4 a, b). For M=Zr, the compound is stabilized by dimerization as evidenced by single‐crystal X‐ray structure analysis. The electrochemical behavior of 3 a, b and 4 a, b was investigated, showing decomposition after oxidation, leading to different redox‐active products.
Alternating Current Electrohydrodynamics Induced Nanoshearing and Fluid Micromixing for Specific Capture of Cancer Cells
Authors: Vaidyanathan Ramanathan , Rauf Sakandar , Dray Eloïse , Shiddiky Muhammad J. A. , Trau Matt
Published: February 2014

We report a new tuneable alternating current (ac) electrohydrodynamics (ac‐EHD) force referred to as “nanoshearing” which involves fluid flow generated within a few nanometers of an electrode surface. This force can be externally tuned via manipulating the applied ac‐EHD field strength. The ability to manipulate ac‐EHD induced forces and concomitant fluid micromixing can enhance fluid transport within the capture domain of the channel (e.g., transport of analytes and hence increase target–sensor interactions). This also provides a new capability to preferentially select strongly bound analytes over nonspecifically bound cells and molecules. To demonstrate the utility and versatility of nanoshearing phenomenon to specifically capture cancer cells, we present proof‐of‐concept data in lysed blood using two microfluidic devices containing a long array of asymmetric planar electrode pairs. Under the optimal experimental conditions, we achieved high capture efficiency (e.g., approximately 90 %; % RSD=2, n=3) with a 10‐fold reduction in nonspecific adsorption of non‐target cells for the detection of whole cells expressing Human Epidermal Growth Factor Receptor 2 (HER2). We believe that our ac‐EHD devices and the use of tuneable nanoshearing phenomenon may find relevance in a wide variety of biological and medical applications.
A Clear‐Cut Example of Selective BpinBdan Activation and Precise Bdan Transfer on Boron Conjugate Addition
Authors: Cid Jessica , Carbó Jorge J. , Fernández Elena
Published: February 2014

Activating the non‐symmetrical BpinBdan diboron reagent with alkoxide leads to the formation of two possible adducts: MeO−→BpinBdan or MeO−→BdanBpin. Experimental and theoretical investigation confirms that the MeO−→Bpin interaction is preferred and thus selective formation of a CBdan bond upon reaction with an activated CC bond.
Synthesis and Structural Data of Tetrabenzo[8]circulene
Authors: Miller Robert W. , Duncan Alexandra K. , Schneebeli Severin T. , Gray Danielle L. , Whalley Adam C.
Published: February 2014

In 1976, the first attempted synthesis of the saddle‐shaped molecule [8]circulene was reported. The next 37 years produced no advancement towards the construction of this complicated molecule. But remarkably, over the last six months, a flurry of progress has been made with two groups reporting independent and strikingly different strategies for the synthesis of [8]circulene derivatives. Herein, we present a third synthetic method, in which we target tetrabenzo[8]circulene. Our approach employs a Diels–Alder reaction and a palladium‐catalyzed arylation reaction as the key steps. Despite calculations describing the instability of [8]circulene, coupled with the reported instability of synthesized derivatives of the parent molecule, the addition of four fused benzenoid rings around the periphery of the molecule provides a highly stable structure. This increased stability over the parent [8]circulene was predicted by using Clar’s theory of aromatic sextets and is a result of the compound becoming fully benzenoid upon incorporation of these additional rings. The synthesized compound exhibits remarkable stability under ambient conditions—even at elevated temperatures—with no signs of decomposition over several months. The solid‐state structure of this compound is significantly twisted compared to the calculated structure primarily as a result of crystal‐packing forces in the solid state. Despite this contortion from the lowest‐energy structure, a range of structural data is presented confirming the presence of localized aromaticity in this large polycyclic aromatic hydrocarbon.
Hetero‐Epitaxial Approach by Using Labile Coordination Sites to Prepare Catenated Metal–Organic Frameworks with High Surface Areas
Authors: Zhu Nianyong , Lennox Matthew J. , Tobin Gerard , Goodman Lisa , Düren Tina , Schmitt Wolfgang
Published: February 2014

A solid‐state approach that takes advantage of the ordered 3D arrangement of active secondary building units allows the preparation of new interlocked MOFs that grow hetero‐epitaxially on the crystal faces of a precursor phase that acts as a “topological blueprint”. The synthetic strategy is exemplified by using rigid acetylene‐based ligands to produce highly augmented CuII acetate‐based MOFs.
NIS‐Assisted Aza‐Friedel–Crafts Reaction with α‐Carbamoysulfides as Precursors of N‐Carbamoylimines
Authors: George Nicolas , Bekkaye Mathieu , Alix Aurélien , Zhu Jieping , Masson Géraldine
Published: February 2014

A general and practical N‐iodosuccinimide (NIS)‐promoted aza‐Friedel–Crafts reaction of various aromatic nucleophiles with N‐acylimines generated in situ from α‐amidosulfides to give a rapid access to highly functionalized amines is described. The newly developed methodology is very mild, fast, efficient, and complementary.
Impact of Obstructive Sleep Apnea on Cardiovascular Outcomes in Patients Treated With Percutaneous Coronary Intervention: Rationale and Design of the Sleep and Stent Study
Authors: Loo Germaine , Koo Chieh‐Yang , Zhang Junjie , Li Ruogu , Sethi Rithi , Ong Thun‐How , Tai Bee‐Choo , Lee Chi‐Hang
Published: February 2014

Elucidating the effects of obstructive sleep apnea (OSA) on cardiovascular outcomes is crucial in risk assessments and therapeutic recommendations for affected individuals. The Sleep and Stent Study is a multicenter observational study investigating the relationships between OSA and cardiovascular outcomes in patients treated with percutaneous coronary intervention (PCI). Eight centers in 5 countries (Singapore, China and Hong Kong, India, Myanmar, and Brazil) are participating in the study, and the recruitment target is 1600 patients. Adult patients age 18 to 80 years who have undergone successful PCI are eligible. Recruited patients will undergo an overnight sleep study using a level‐3 portable diagnostic device before hospital discharge. The sleep tracings will be analyzed by a certified sleep technologist and audited by a sleep physician, both of whom will be blinded to other study data. The patients will be divided into 2 groups based on apnea‐hypopnea index (AHI): OSA (AHI ≥15) and non‐OSA (AHI <15) groups. The primary study endpoint of cardiovascular death, myocardial infarction, stroke, and unplanned revascularization will be compared between the OSA and non‐OSA groups at a median follow‐up of 2 years. Secondary endpoints include all‐cause mortality, target‐vessel revascularization, stent thrombosis, and hospitalization for heart failure. As of December 31, 2013, a total of 1358 patients have been recruited. Based on the complete preliminary results of the first 785 recruited patients, the prevalence of OSA was 48.3%. We expect the follow‐up for primary endpoint to be completed in late 2015; study results will be presented in 2016.