bluuebunny/crossref_metadata_2025 huggingface dataset:
Water mass mixing: The dominant control on the zinc distribution in the North Atlantic Ocean
Authors: Roshan Saeed , Wu Jingfeng
Published: July 2015

Dissolved zinc (dZn) concentration was determined in the North Atlantic during the U.S. GEOTRACES 2010 and 2011 cruise (GOETRACES GA03). A relatively poor linear correlation (R2 = 0.756) was observed between dZn and silicic acid (Si), the slope of which was 0.0577 nM/µmol/kg. We attribute the relatively poor dZn‐Si correlation to the following processes: (a) differential regeneration of zinc relative to silicic acid, (b) mixing of multiple water masses that have different Zn/Si, and (c) zinc sources such as sedimentary or hydrothermal. To quantitatively distinguish these possibilities, we use the results of Optimum Multi‐Parameter Water Mass Analysis by Jenkins et al. (2015) to model the zinc distribution below 500 m. We hypothesized two scenarios: conservative mixing and regenerative mixing. The first scenario (conservative) could be modeled to results in a correlation with observations with a R2 = 0.846. In the second scenario, we took a Si‐related regeneration into account, which could model the observations with a R2 = 0.867. Through this regenerative mixing scenario, we estimated a Zn/Si = 0.0548 nM/µmol/kg that may be more realistic than linear regression slope due to accounting for process b. However, this did not improve the model substantially (R2 = 0.867 versus0.846), which may indicate the insignificant effect of remineralization on the zinc distribution in this region. The relative weakness in the model‐observation correlation (R2~0.85 for both scenarios) implies that processes (a) and (c) may be plausible. Furthermore, dZn in the upper 500 m exhibited a very poor correlation with apparent oxygen utilization, suggesting a minimal role for the organic matter‐associated remineralization process.
Unipolar and bipolar pulses emitted during the development of lightning flashes
Authors: Kašpar Petr , Santolík Ondřej , Kolmašová Ivana
Published: July 2015

Both unipolar and bipolar magnetic or electric field pulses have been observed during preparatory stages of a lightning flash. We introduce a new simple analytical model to describe both kinds of pulses. We show how the polarity overshoot depends on the parameters of the model, including the propagation velocity of the current pulse, the step length, and the injected current waveshape. We observe that the expression for the radiation part of the magnetic field can be decomposed into two time‐shifted terms with opposite polarities. The time shift of the two terms is determined by the overall propagation time of the current pulse. The model well corresponds not only to observations of the bipolar preliminary breakdown pulses at time scales of tens of microseconds but also to both unipolar and bipolar dart‐stepped leader pulses at submicrosecond time scales.
Comparison and evaluation of the MODIS Collection 6 aerosol data in China
Authors: Tao Minghui , Chen Liangfu , Wang Zifeng , Tao Jinhua , Che Huizheng , Wang Xinhui , Wang Yang
Published: July 2015

Several important improvements have been made in recent Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6 aerosol retrievals, but few regional validations are conducted. We compared Deep Blue (DB) and Dark Target (DT) retrievals over China and evaluated their performance with ground observations. Sampling frequency of DB was much higher than that of DT, which was mainly caused by unavailable retrieval of DT in bright surface and heavy pollution conditions. It is found that merged aerosol optical depth (AOD) will miss some cases if it was determined only by vegetation density. Collocated comparison shows that DT AOD was substantially higher than DB with seasonal difference exceeding 0.3–0.4 over eastern China. However, when all available retrievals were considered, DT AOD was obviously lower than DB in all the seasons except spring due to their large difference in spatial coverage in high‐AOD conditions. DB can well reveal spatial extent of the widespread haze pollution while there were few values in DT. More than one half of the situations with AOD > 1.0 was missed by DT, which largely underestimated the common regional haze pollution in eastern China. Ground validations show that DT tended to overestimate the aerosol loading by underestimation of the surface contribution and single scattering albedo of aerosols. DB performed generally well with higher accuracy in northern China but exhibited obvious underestimation in northwestern and southern China. Despite of slight decrease in accuracy, DB retrievals with all quality enable a large increase in spatial coverage, especially when dense haze clouds existed.
Estimating errors in cloud amount and cloud optical thickness due to limited spatial sampling using a satellite imager as a proxy for nadir‐view sensors
Authors: Liu Yinghui
Published: July 2015

Cloud climatologies from space‐based active sensors have been used in climate and other studies without their uncertainties specified. This study quantifies the errors in monthly mean cloud amount and optical thickness due to the limited spatial sampling of space‐based active sensors. Nadir‐view observations from a satellite imager, the Moderate Resolution Imaging Spectroradiometer (MODIS), serve as a proxy for those active sensors and observations within 10° of the sensor's nadir view serve as truth for data from 2003 to 2013 in the Arctic. June–July monthly mean cloud amount and liquid water and ice cloud optical thickness from MODIS for both observations are calculated and compared. Results show that errors increase with decreasing sample numbers for monthly means in cloud amount and cloud optical thickness. The root‐mean‐square error of monthly mean cloud amount from nadir‐view observations increases with lower latitudes, with 0.7% (1.4%) at 80°N and 4.2% (11.2%) at 60°N using data from 2003 to 2013 (from 2012). For a 100 km resolution Equal‐Area Scalable Earth Grid (EASE‐Grid) cell of 1000 sample numbers, the absolute differences in these two monthly mean cloud amounts are less than 6.5% (9.0%, 11.5%) with an 80 (90, 95)%chance; such differences decrease to 4.0% (5.0%, 6.5%) with 5000 sample numbers. For a 100 km resolution EASE‐Grid of 1000 sample numbers, the absolute differences in these two monthly mean cloud optical thicknesses are less than 2.7 (3.8) with a 90% chance for liquid water cloud (ice cloud); such differences decrease to 1.3 (1.0) for 5000 sample numbers. The uncertainties in monthly mean cloud amount and optical thickness estimated in this study may provide useful information for applying cloud climatologies from active sensors in climate studies and suggest the need for future spaceborne active sensors with a wide swath.
Versatile Self‐Cleaning Coating Production Through Sol–Gel Chemistry
Authors: Power A. C. , Barrett A. , Abubakar J. , Suarez L. J. , Ryan L. , Wencel D. , Sullivan T. , Regan F.
Published: July 2015

The performance of optical devices is dependent on their optical transparency (OT). This is evident when such devices are exposed to environmental conditions that can reduce OT. The development of a robust, transparent and self‐cleaning coating is highly desirable, for applications likeoptical windows and solar panels. This work reports the design of such coatings based on a hydrophobic thin film fabricated using a sol‐gel process. Coating properties were optimised by modification of the surface topography of the coatings, achieved by the incorporation of silica nanoparticles(NPs). The coating was characterised by water contact angle(WCA), scanning electron microscopy(SEM) and white light interferometry (WLI). The efficacy and robustness of the coating foroptical application was assessed.
Solid Solution Domains at Phase Transition Front of LixNi0.5Mn1.5O4
Authors: Komatsu Hideyuki , Arai Hajime , Koyama Yukinori , Sato Kenji , Kato Takeharu , Yoshida Ryuji , Murayama Haruno , Takahashi Ikuma , Orikasa Yuki , Fukuda Katsutoshi , Hirayama Tsukasa , Ikuhara Yuichi , Ukyo Yoshio , Uchimoto Yoshiharu , Ogumi Zempachi
Published: July 2015

Nickel‐substituted manganese spinel LiNi0.5Mn1.5O4 (LNMO) is a promising 5 V class positive electrode material for lithium‐ion batteries. As micron‐sized LNMO particles show high rate capability in its two‐phase coexistence regions, the phase transition mechanism is of great interest in understanding the electrode behavior at high rates. Here, the phase transition dynamics of LixNi0.5Mn1.5O4 is elucidated on high rate charging–discharging using operando time‐resolved X‐ray diffraction (TR‐XRD). The TR‐XRD results indicate the existence of intermediate states, in addition to the thermodynamically stable phases, and it is shown that the origin of such intermediate states is ascribed to the solid‐solution domains at the phase transition front, as supported by the analysis using transmission electron microscopy coupled with electron energy‐loss spectroscopy. The phase transition pathways dependent on the reaction rate are shown, together with possible explanation for this unique transition behavior.
Matter‐antimatter asymmetry ‐ aspects at low energy
Authors: Willmann Lorenz , Jungmann Klaus
Published: July 2015

The apparent dominance of matter over antimatter in our universe is an obvious and puzzling fact which cannot be adequately explained in present physical frameworks that assume matter‐antimatter symmetry at the big bang. However, our present knowledge of starting conditions and of known sources of CP violation are both insufficient to explain the observed asymmetry. Therefore ongoing research on matter‐antimatter differences is strongly motivated as well as attempts to identify viable new mechanisms that could create the present asymmetry. Here we concentrate on possible precision experiments at low energies towards a resolution of this puzzle.

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Neue Ansätze zur Empfindlichkeitssteigerung in der biomolekularen NMR‐Spektroskopie
Authors: Ardenkjaer‐Larsen Jan‐Henrik , Boebinger Gregory S. , Comment Arnaud , Duckett Simon , Edison Arthur S. , Engelke Frank , Griesinger Christian , Griffin Robert G. , Hilty Christian , Maeda Hidaeki , Parigi Giacomo , Prisner Thomas , Ravera Enrico , van Bentum Jan , Vega Shimon , Webb Andrew , Luchinat Claudio , Schwalbe Harald , Frydman Lucio
Published: July 2015

Im Frühling 2013 versammelten sich NMR‐Spektroskopiker am Weizmann‐Institut in Israel, um neue Ansätze zur Verbesserung der Empfindlichkeit von NMR‐Experimenten zu diskutieren, besonders im Hinblick auf Experimente an biomolekularen Systemen. Der vorliegende Aufsatz ist von vielen Autoren mit unterschiedlichem fachlichem Hintergrund verfasst worden; er beschreibt den Stand der Forschung auf diesem Gebiet, wie er im Rahmen des Treffens diskutiert wurde. Es werden Ansätze für Ultra‐Hochfeld‐NMR‐Spektroskopie, für neuartige Techniken der NMR‐Detektion, für Prinzipien und Methoden der Kernhyperpolarisation, aber auch für neue Probenpräparationsmethoden diskutiert. Diese Ansätze verbessern die Empfindlichkeit von NMR‐Experimenten im Festkörper und in Lösung, sind voneinander unabhängig und können sich in ihren Auswirkungen multiplizieren. Auch wenn in allen genannten Bereichen bereits substanzielle Verbesserungen erzielt wurden, ist doch noch eine weite Strecke zu überwinden, um an die Empfindlichkeiten von optischen und elektronischen Spektroskopien heranzureichen. Diese Probleme und erste Lösungsansätze werden ebenfalls diskutiert.
Über die Rolle von Metallen in Elektrokatalysatoren auf Basis von stickstoffdotiertem Kohlenstoff für die Sauerstoffreduktion
Authors: Masa Justus , Xia Wei , Muhler Martin , Schuhmann Wolfgang
Published: July 2015

Der Begriff des metallfreien Katalysators bezeichnet Kohlenstoffmaterialien, die mit nichtmetallischen Elementen modifiziert sind. Manche Katalysatoren, die als metallfrei gelten, werden jedoch unter Verwendung von metallhaltigen Vorstufen hergestellt. Spuren von Metallen in stickstoffdotiertem Kohlenstoff (“nitrogen‐doped carbon”, NC) spielen eine umstrittene Rolle bei der Sauerstoffreduktionsreaktion (ORR). Es wird eine Definition für tatsächlich metallfreie Katalysatoren vorgeschlagen, und der Unterschied zwischen stickstoffdotiertem Kohlenstoff und M‐Nx/C wird herausgearbeitet. Metallverunreinigungen, die typischerweise unterhalb der Nachweisgrenze von XPS, XRD und EDX liegen, beschleunigen deutlich die ORR. Durch Vergiftungstests, bei denen die Metallionen maskiert werden, wird deutlich, dass Metallreste die elektronische Struktur des NC verändern können oder selbst als aktive Zentren agieren. Die Vorzüge von sowohl M‐Nx/C‐ als auch NC‐Systemen werden diskutiert, um die Weiterentwicklung von Nicht‐Edelmetall‐Katalysatoren für die ORR voranzutreiben.
Transition‐Metal‐Free α‐Arylation of Enolizable Aryl Ketones and Mechanistic Evidence for a Radical Process
Authors: Pichette Drapeau Martin , Fabre Indira , Grimaud Laurence , Ciofini Ilaria , Ollevier Thierry , Taillefer Marc
Published: July 2015

The α‐arylation of enolizable aryl ketones can be carried out with aryl halides under transition‐metal‐free conditions using KOtBu in DMF. The α‐aryl ketones thus obtained can be used for step‐ and cost‐economic syntheses of fused heterocycles and Tamoxifen. Mechanistic studies demonstrate the synergetic role of base and solvent for the initiation of the radical process.
Observation of Body‐Centered Cubic Gold Nanocluster
Authors: Liu Chao , Li Tao , Li Gao , Nobusada Katsuyuki , Zeng Chenjie , Pang Guangsheng , Rosi Nathaniel L. , Jin Rongchao
Published: July 2015

The structure of nanoparticles plays a critical role in dictating their material properties. Gold is well known to adopt face‐centered cubic (fcc) structure. Herein we report the first observation of a body‐centered cubic (bcc) gold nanocluster composed of 38 gold atoms protected by 20 adamantanethiolate ligands and two sulfido atoms ([Au38S2(SR)20], where R=C10H15) as revealed by single‐crystal X‐ray crystallography. This bcc structure is in striking contrast with the fcc structure of bulk gold and conventional Au nanoparticles, as well as the bi‐icosahedral structure of [Au38(SCH2CH2Ph)24]. The bcc nanocluster has a distinct HOMO–LUMO gap of ca. 1.5 eV, much larger than the gap (0.9 eV) of the bi‐icosahedral [Au38(SCH2CH2Ph)24]. The unique structure of the bcc gold nanocluster may be promising in catalytic applications.
Formkontrollierte Synthese und Selbstsortierung kovalent‐organischer Käfigverbindungen
Authors: Klotzbach Stefanie , Beuerle Florian
Published: July 2015

Das Konzept der direktionalen Bindungen ist ein leistungsstarkes Hilfsmittel zur präzisen Kontrolle von Form und Stöchiometrie für dreidimensionale Objekte, die aus starren Baueinheiten unter dynamisch‐kovalenten Bedingungen aufgebaut werden. Cokondensationen von Catechol‐funktionalisierten Tribenzotriquinacen‐Derivaten mit einem jeweiligen Winkel von 90° zwischen den reaktiven Positionen und Diboronsäuren mit Bisswinkeln von jeweils 60°, 120° und 180° führten zu einer effizienten und vorhersagbaren Bildung von bipyramidalen, tetraedrischen und kubischen kovalent‐organischen Käfigverbindungen. Untersuchungen zur Selbstsortierung von ternären Mischungen, die jeweils zwei konkurrierende Boronsäuren enthielten, zeigten in Abhängigkeit von der relativen Stabilität der getrennten Käfige im Vergleich mit möglichen Drei‐Komponenten‐Systemen entweder narzisstisches oder soziales Verhalten.
NiSe Nanowire Film Supported on Nickel Foam: An Efficient and Stable 3D Bifunctional Electrode for Full Water Splitting
Authors: Tang Chun , Cheng Ningyan , Pu Zonghua , Xing Wei , Sun Xuping
Published: July 2015

Active and stable electrocatalysts made from earth‐abundant elements are key to water splitting for hydrogen production through electrolysis. The growth of NiSe nanowire film on nickel foam (NiSe/NF) in situ by hydrothermal treatment of NF using NaHSe as Se source is presented. When used as a 3D oxygen evolution electrode, the NiSe/NF exhibits high activity with an overpotential of 270 mV required to achieve 20 mA cm−2 and strong durability in 1.0 M KOH, and the NiOOH species formed at the NiSe surface serves as the actual catalytic site. The system is also highly efficient for catalyzing the hydrogen evolution reaction in basic media. This bifunctional electrode enables a high‐performance alkaline water electrolyzer with 10 mA cm−2 at a cell voltage of 1.63 V.
Biomineralization of a Cadmium Chloride Nanocrystal by a Designed Symmetrical Protein
Authors: Voet Arnout R. D. , Noguchi Hiroki , Addy Christine , Zhang Kam Y. J. , Tame Jeremy R. H.
Published: July 2015

We have engineered a metal‐binding site into the novel artificial β‐propeller protein Pizza. This new Pizza variant carries two nearly identical domains per polypeptide chain, and forms a trimer with three‐fold symmetry. The designed single metal ion binding site lies on the symmetry axis, bonding the trimer together. Two copies of the trimer associate in the presence of cadmium chloride in solution, and very high‐resolution X‐ray crystallographic analysis reveals a nanocrystal of cadmium chloride, sandwiched between two trimers of the protein. This nanocrystal, containing seven cadmium ions lying in a plane and twelve interspersed chloride ions, is the smallest reported to date. Our results indicate the feasibility of using rationally designed symmetrical proteins to biomineralize nanocrystals with useful properties.
Deutlich unterschiedliche Mechanismen der Wasserstoffatomabstraktion aus Methan und Wasser durch den heteronuklearen Oxidcluster [Ga2MgO4].+
Authors: Li Jilai , Wu Xiao‐Nan , Zhou Shaodong , Tang Shiya , Schlangen Maria , Schwarz Helmut
Published: July 2015

Die thermischen Reaktionen des heteronuklearen Oxidclusters [Ga2MgO4].+ mit Methan und Wasser wurden mit modernsten Gasphasenexperimenten und quantenchemischen Rechnungen untersucht. Im Gegensatz zur H‐Abstraktion aus Methan folgt die Aktivierung von Wasser einem protonengekoppelten Elektronentransfermechanismus (proton‐coupled electron transfer, PCET); ihm ist die deutlich höhere Reaktivität gegenüber der starken O‐H‐Bindung geschuldet. Die Erkenntnisse dieser Studie vertiefen das mechanistische Verständnis, wie inerte R‐H‐Bindungen durch Metalloxide gespalten werden können.
Inhibiting an Epoxide Hydrolase Virulence Factor from Pseudomonas aeruginosa Protects CFTR
Authors: Bahl Christopher D. , Hvorecny Kelli L. , Bomberger Jennifer M. , Stanton Bruce A. , Hammock Bruce D. , Morisseau Christophe , Madden Dean R.
Published: July 2015

Opportunistic pathogens exploit diverse strategies to sabotage host defenses. Pseudomonas aeruginosa secretes the CFTR inhibitory factor Cif and thus triggers loss of CFTR, an ion channel required for airway mucociliary defense. However, the mechanism of action of Cif has remained unclear. It catalyzes epoxide hydrolysis, but there is no known role for natural epoxides in CFTR regulation. It was demonstrated that the hydrolase activity of Cif is strictly required for its effects on CFTR. A small‐molecule inhibitor that protects this key component of the mucociliary defense system was also uncovered. These results provide a basis for targeting the distinctive virulence chemistry of Cif and suggest an unanticipated role of physiological epoxides in intracellular protein trafficking.
Enhanced Hydrogen Production from DNA‐Assembled Z‐Scheme TiO2–CdS Photocatalyst Systems
Authors: Ma Ke , Yehezkeli Omer , Domaille Dylan W. , Funke Hans H. , Cha Jennifer N.
Published: July 2015

A wide range of inorganic nanostructures have been used as photocatalysts for generating H2. To increase activity, Z‐scheme photocatalytic systems have been implemented that use multiple types of photoactive materials and electron mediators. Optimal catalysis has previously been obtained by interfacing different materials through aggregation or epitaxial nucleation, all of which lowers the accessible active surface area. DNA has now been used as a structure‐directing agent to organize TiO2 and CdS nanocrystals. A significant increase in H2 production compared to CdS or TiO2 alone was thus observed directly in solution with no sacrificial donors or applied bias. The inclusion of benzoquinone (BQ) equidistant between the TiO2 and CdS through DNA assembly further increased H2 production. While the use of a second quinone in conjunction with BQ showed no more improvement, its location within the Z‐scheme was found to strongly influence catalysis.
A pH‐Responsive Carrier System that Generates NO Bubbles to Trigger Drug Release and Reverse P‐Glycoprotein‐Mediated Multidrug Resistance
Authors: Chung Ming‐Fan , Liu Hung‐Yi , Lin Kun‐Ju , Chia Wei‐Tso , Sung Hsing‐Wen
Published: July 2015

Multidrug resistance (MDR) resulting from the overexpression of drug transporters such as P‐glycoprotein (Pgp) increases the efflux of drugs and thereby limits the effectiveness of chemotherapy. To address this issue, this work develops an injectable hollow microsphere (HM) system that carries the anticancer agent irinotecan (CPT‐11) and a NO‐releasing donor (NONOate). Upon injection of this system into acidic tumor tissue, environmental protons infiltrate the shell of the HMs and react with their encapsulated NONOate to form NO bubbles that trigger localized drug release and serve as a Pgp‐mediated MDR reversal agent. The site‐specific drug release and the NO‐reduced Pgp‐mediated transport can cause the intracellular accumulation of the drug at a concentration that exceeds the cell‐killing threshold, eventually inducing its antitumor activity. These results reveal that this pH‐responsive HM carrier system provides a potentially effective method for treating cancers that develop MDR.
Catalytic Ring Expansion of Cyclic Hemiaminals for the Synthesis of Medium‐Ring Lactams
Authors: Zhao Wanxiang , Qian Hui , Li Zigang , Sun Jianwei
Published: July 2015

A mild and efficient intermolecular ring‐expansion approach was developed for the synthesis of medium‐ring lactams by using siloxy alkynes. Key to success is the suitable combination of a superior catalyst and an exceptional nitrogen‐protecting group. Control experiments indicated that the reaction is remarkably selective toward the desired lactam formation, even with many possible non‐productive pathways.
α‐Peptide–Oligourea Chimeras: Stabilization of Short α‐Helices by Non‐Peptide Helical Foldamers
Authors: Fremaux Juliette , Mauran Laura , Pulka‐Ziach Karolina , Kauffmann Brice , Odaert Benoit , Guichard Gilles
Published: July 2015

Short α‐peptides with less than 10 residues generally display a low propensity to nucleate stable helical conformations. While various strategies to stabilize peptide helices have been previously reported, the ability of non‐peptide helical foldamers to stabilize α‐helices when fused to short α‐peptide segments has not been investigated. Towards this end, structural investigations into a series of chimeric oligomers obtained by joining aliphatic oligoureas to the C‐ or N‐termini of α‐peptides are described. All chimeras were found to be fully helical, with as few as 2 (or 3) urea units sufficient to propagate an α‐helical conformation in the fused peptide segment. The remarkable compatibility of α‐peptides with oligoureas described here, along with the simplicity of the approach, highlights the potential of interfacing natural and non‐peptide backbones as a means to further control the behavior of α‐peptides.
Switching and Conformational Fixation of Amides Through Proximate Positive Charges
Authors: Bartuschat Amelie L. , Wicht Karina , Heinrich Markus R.
Published: July 2015

Tertiary amides, which usually occur as cis/trans mixtures, can be effectively shifted to the cis conformation by placing a positive charge in close proximity to the amide carbonyl. This effect was used to prepare cis‐configured prolyl amides and to facilitate a strongly rotamer‐dependent radical cyclization.
Direct Observation of the Reversible Two‐State Unfolding and Refolding of an α/β Protein by Single‐Molecule Atomic Force Microscopy
Authors: He Chengzhi , Hu Chunguang , Hu Xiaodong , Hu Xiaotang , Xiao Adam , Perkins Thomas T. , Li Hongbin
Published: July 2015

Directly observing protein folding in real time using atomic force microscopy (AFM) is challenging. Here the use of AFM to directly monitor the folding of an α/β protein, NuG2, by using low‐drift AFM cantilevers is demonstrated. At slow pulling speeds (<50 nm s−1), the refolding of NuG2 can be clearly observed. Lowering the pulling speed reduces the difference between the unfolding and refolding forces, bringing the non‐equilibrium unfolding–refolding reactions towards equilibrium. At very low pulling speeds (ca. 2 nm s−1), unfolding and refolding were observed to occur in near equilibrium. Based on the Crooks fluctuation theorem, we then measured the equilibrium free energy change between folded and unfolded states of NuG2. The improved long‐term stability of AFM achieved using gold‐free cantilevers allows folding–unfolding reactions of α/β proteins to be directly monitored near equilibrium, opening the avenue towards probing the folding reactions of other mechanically important α/β and all‐β elastomeric proteins.
Shape‐Controlled Synthesis and Self‐Sorting of Covalent Organic Cage Compounds
Authors: Klotzbach Stefanie , Beuerle Florian
Published: July 2015

The directional bonding approach is a powerful tool to rationally control both shape and stoichiometry of three‐dimensional objects built from rigid building blocks under dynamic covalent conditions. Co‐condensation of catechol‐functionalized tribenzotriquinacene derivatives which have 90° angles between the reactive sites and diboronic acids with bite angles of 60°, 120°, and 180°, led to the efficient formation of, respectively, bipyramidal, tetrahedral, or cubic covalent organic cage compounds in a predictable manner. Investigations on the self‐sorting of ternary mixtures containing two competitive boronic acids revealed either narcissistic or social self‐sorting depending on the stability of the segregated cages relative to feasible three‐component assemblies.
Host–Guest Complexation of Perethylated Pillar[5]arene with Alkanes in the Crystal State
Authors: Ogoshi Tomoki , Sueto Ryuta , Yoshikoshi Kumiko , Sakata Yoko , Akine Shigehisa , Yamagishi Tada‐aki
Published: July 2015

Activated perethylated pillar[5]arene crystals show an unexpected alkane‐shape‐ and ‐length‐selective gate‐opening behavior. Activated crystals were obtained upon removing solvents from perethylated pillar[5]arene crystals by heating. The activated crystals could quantitatively take up n‐alkanes with carbon chains containing more than five carbon atoms as a consequence of their gate‐opening pressure. As the chain length of the n‐alkanes increased, the gate pressure decreased. A transformation into a herringbone structure was induced when n‐hexane was used as a guest. By contrast, cyclic and branched alkanes were not taken up and could not induce a crystal transformation because they were too large to fit in the cavities of the pillar[5]arene. Alkane‐shape‐selective molecular recognition of pillar[5]arenes in the solution state was translated into the vapor/crystal state.
Distinct Mechanistic Differences in the Hydrogen‐Atom Transfer from Methane and Water by the Heteronuclear Oxide Cluster [Ga2MgO4].+
Authors: Li Jilai , Wu Xiao‐Nan , Zhou Shaodong , Tang Shiya , Schlangen Maria , Schwarz Helmut
Published: July 2015

The thermal reactions of the heteronuclear oxide cluster [Ga2MgO4].+ with methane and water have been studied using state‐of‐the‐art gas‐phase experiments in conjunction with quantum‐chemical calculations. The significant reactivity differences, favoring activation of the strong OH bond, can be ascribed to a proton‐coupled electron transfer (PCET) mechanism operative in the activation of water. This study deepens our mechanistic understanding on how inert RH bonds are cleaved by metal oxides.
N‐Heterocyclic Olefins as Organocatalysts for Polymerization: Preparation of Well‐Defined Poly(propylene oxide)
Authors: Naumann Stefan , Thomas Anthony W. , Dove Andrew P.
Published: July 2015

The metal‐free polymerization of propylene oxide (PO) using a special class of alkene—N‐heterocyclic olefins (NHOs)—as catalysts is described. Manipulation of the chemical structure of the NHO organocatalyst allows for the preparation of the poly(propylene oxide) in high yields with high turnover (TON>2000), which renders this the most active metal‐free system for the polymerization of PO reported to date. The resulting polyether displays predictable end groups, molar mass, and a low dispersity (ĐM<1.09). NHOs with an unsaturated backbone are essential for polymerization to occur, while substitution at the exocyclic carbon atom has an impact on the reaction pathway and ensures the suppression of side reactions.
Cationic Iridium/S‐Me‐BIPAM‐Catalyzed Direct Asymmetric Intermolecular Hydroarylation of Bicycloalkenes
Authors: Shirai Tomohiko , Yamamoto Yasunori
Published: July 2015

Highly enantioselective cationic iridium‐catalyzed hydroarylation of bicycloalkenes, by carbonyl‐directed CH bond cleavage, was accomplished using a newly synthesized sulfur‐linked bis(phosphoramidite) ligand (S‐Me‐BIPAM). The reaction provides alkylated acetophenone or benzamide derivatives in moderate to excellent yields and good to excellent enantioselectivities. Notably, the hydroarylation reaction of 2‐norbornene with N,N‐dialkylbenzamide proceeds with excellent enantioselectivity (up to 99 % ee) and high selectivity for the mono‐ortho‐alkylation product.
Regulation of the NADH pool and NADH/NADPH ratio redistributes acetoin and 2,3‐butanediol proportion in Bacillus subtilis
Authors: Bao Teng , Zhang Xian , Zhao Xiaojing , Rao Zhiming , Yang Taowei , Yang Shangtian
Published: July 2015

Bacillus subtilis produces acetoin as a major product along with several NADH‐dependent byproducts, especially 2,3‐butanediol. In this study, the down‐regulation of the NADH pool and the redistribution of NADH/NADPH were targeted using external and genetic processes, as a means by which to redistribute the metabolic flux in favor of acetoin synthesis. First, it was found that the use of carbon sources of different oxidation states resulted in very different intracellular NADH/NAD+ ratios that dictated the total process yield of acetoin. A mixture of glucose and gluconate as substrate produced a relatively low NADH/NAD+ ratio, and resulted in an increase in acetoin production while byproducts significantly decreased. Metabolic engineering methods using glucose as a substrate could yield a similar effect. Acetoin production was significantly enhanced by overexpression of the oxidative pentose phosphate pathway: increased expression of glucose‐6‐phosphate dehydrogenase resulted in a decrease in the intracellular NADH/NADPH ratio (1.9‐fold) and NADH/NAD+ ratio (1.7‐fold). In fed‐batch culture the engineered strain yielded an acetoin concentration of 43.3 g L–1, while the production of 2,3‐butanediol was only 1.7 g L–1. The concept of the manipulation of cofactor levels to redistribute carbon flux by external and genetic means as explored in this paper provides a novel strategy for improving industrial acetoin fermentation.
Five-year results of a randomized clinical trial of conventional surgery, endovenous laser ablation and ultrasound-guided foam sclerotherapy in patients with great saphenous varicose veins
Authors: van der Velden S K , Biemans A A M , De Maeseneer M G R , Kockaert M A , Cuypers P W , Hollestein L M , Neumann H A M , Nijsten T , van den Bos R R
Published: July 2015

Background

A variety of techniques exist for the treatment of patients with great saphenous vein (GSV) varicosities. Few data exist on the long-term outcomes of these interventions.

Methods

Patients undergoing conventional surgery, endovenous laser ablation (EVLA) and ultrasound-guided foam sclerotherapy (UGFS) for GSV varicose veins were followed up for 5 years. Primary outcome was obliteration or absence of the treated GSV segment; secondary outcomes were absence of GSV reflux, and change in Chronic Venous Insufficiency quality-of-life Questionnaire (CIVIQ) and EuroQol – 5D (EQ-5D™) scores.

Results

A total of 224 legs were included (69 conventional surgery, 78 EVLA, 77 UGFS), 193 (86·2 per cent) of which were evaluated at final follow-up. At 5 years, Kaplan–Meier estimates of obliteration or absence of the GSV were 85 (95 per cent c.i. 75 to 92), 77 (66 to 86) and 23 (14 to 33) per cent in the conventional surgery, EVLA and UGFS groups respectively. Absence of above-knee GSV reflux was found in 85 (73 to 92), 82 (72 to 90) and 41 (30 to 53) per cent respectively. CIVIQ scores deteriorated over time in patients in the UGFS group (0·98 increase per year, 95 per cent c.i. 0·16 to 1·79), and were significantly worse than those in the EVLA group (−0·44 decrease per year, 95 per cent c.i. −1·22 to 0·35) (P = 0·013). CIVIQ scores for the conventional surgery group did not differ from those in the EVLA and UGFS groups (0·44 increase per year, 95 per cent c.i. −0·41 to 1·29). EQ-5D™ scores improved equally in all groups.

Conclusion

EVLA and conventional surgery were more effective than UGFS in obliterating the GSV 5 years after intervention. UGFS was associated with substantial rates of GSV reflux and inferior CIVIQ scores compared with EVLA and conventional surgery. Registration number: NCT00529672 (http://www.clinicaltrials.gov).
SapWin 4.0–a new simulation program for electrical engineering education using symbolic analysis
Authors: Grasso F. , Luchetta A. , Manetti S. , Piccirilli M. C. , Reatti A.
Published: July 2015

The paper presents the main capabilities and the possible applications in the teaching area of Electrical/Electronic Engineering of a software system developed by the authors and aimed at simulating analog linear (or linearized) circuits. The work is the enrichment, enhancement and extension of some programs developed by the same authors along the last two decades and distributed in many schools, institutions, industries, and research centers for different purposes. The feedback (in terms of suggestions, corrections, and improvement requests) has been collected to generate a completely renewed software that could definitely become a really efficient tool in the field of analog circuits, also filling the gap which still exists in the use of very famous and classical circuit simulators (as, for instance, the SPICE family). The application of the past experience involves several courses, as it will be described in the final sections of paper. © 2015 Wiley Periodicals, Inc. Comput. Appl. Eng. Educ. 24:44–57, 2016; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21671
Optimal management of cervical cancer in HIV‐positive patients: a systematic review
Authors: Ntekim Atara , Campbell Oladapo , Rothenbacher Dietrich
Published: July 2015

The clinical management of cervical cancer in HIV‐positive patients has challenges mainly due to the concerns on immune status. At present, their mode of management is similar to HIV‐seronegative patients involving the use of chemotherapy and radiotherapy concurrently as indicated. HIV infection, cancer, radiotherapy, and chemotherapy lower immunity through reduction in CD4 cell counts. At present there are no treatment guidelines for HIV‐positive patients. This study was done to systematically review the literature on cervical cancer management in HIV‐positive patients and treatment outcomes. A systematic literature search was done in the major databases to identify studies on the management of HIV‐positive patients with cervical cancer. Identified studies were assessed for eligibility and inclusion in the review following the guidelines of The Cochrane Handbook for Systematic Reviews and CRD's (Centre for Reviews and Dissemination) guidance for undertaking reviews in health care. Eight eligible studies were identified from the literature. Three of them were prospective while five were retrospective studies. Notably, the average age at diagnosis of cervical cancer in HIV‐positive patients was a decade lower than in seronegative patients. There was no difference in distribution of stages of disease at presentation between HIV‐positive and negative patients. Mild acute toxicity (Grades 1 and 2) was higher in HIV‐positive patients than in HIV‐negative patients in hematopoietic system. In the grades 3 and 4 reactions, anemia was reported in 4% versus 2% while gastrointestinal reactions were reported in 5% versus 2% respectively. In general, patients who were started early on HAART had higher rates of treatment completion. The study supports the suggestion that HAART should be commenced early at cervical cancer diagnosis in HIV‐positive patients diagnosed with cervical cancer to ensure less toxicity and better treatment compliance.
The Pyridyl Functional Groups Guide the Formation of Pd Nanoparticles Inside A Porous Poly(4‐Vinyl‐Pyridine)
Authors: Groppo Elena , Agostini Giovanni , Borfecchia Elisa , Lazzarini Andrea , Liu Wei , Lamberti Carlo , Giannici Francesco , Portale Giuseppe , Longo Alessandro
Published: July 2015

The reactivity of palladium acetate inside a poly(4‐vinylpyridine‐co‐divinylbenzene) polymer is strongly influenced by the establishment of interaction between the Pd precursor and the pyridyl functional group in the polymer. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and simultaneous X‐ray absorption near edge structure (XANES) and small angle X‐ray scattering (SAXS) techniques have been applied to monitor the reactivity of palladium acetate in the presence of H2 and CO as a function of temperature. H2 reduces palladium acetate to Pd nanoparticles and acetic acid. The pyridyl groups in the polymer play a vital role both in stabilizing the formed acetic acid, thus allowing its detection by means of DRIFTS, and the final Pd nanoparticles, which are extremely small and mono‐dispersed. On the contrary, CO does not reduce palladium acetate. Rather, it forms Pd2+ carbonyl adducts, which favor the detachment of the acetate ligands and their thermal degradation. These adducts are well observable by means of SAXS because they cause an important local change of the electronic density.
Does the Surface Structure of Oxide Affect the Strong Metal–Support Interaction with Platinum? Platinum on Fe3O4(0 0 1) versus Fe3O4(1 1 1)
Authors: Zhang Ke , Shaikhutdinov Shamil , Freund Hans‐Joachim
Published: July 2015

We studied the structure and thermal stability of Pt deposited on a Fe3O4(0 0 1) thin film to make a comparison with the Pt/Fe3O4(1 1 1) system that shows a strong metal–support interaction (SMSI) through encapsulation. Pt adatoms interact strongly with the (√2×√2)R45°‐reconstructed Fe3O4(0 0 1) surface and adsorb monoatomically on the “narrow” sites. Metal sintering sets in only above 700 K to result in cuboid Pt nanoparticles exposing primarily (1 0 0) and (1 1 0) facets. Concomitantly, CO adsorption on Pt is fully suppressed as a result of the SMSI. The results provided strong evidence that the Pt nanoparticles on Fe3O4(0 0 1) are encapsulated by an FeO(1 1 1) layer in the same manner as observed for hemispherical Pt particles on Fe3O4(1 1 1). The comparison suggests that the SMSI effect through encapsulation is insensitive to the surface structure of the oxide, although the latter strongly affects the particle morphology.
N‐Heterocyclic Carbene–Pd Polymers as Reusable Precatalysts for Cyanation and Ullmann Homocoupling of Aryl Halides: The Role of Solvent in Product Distribution
Authors: Karimi Babak , Vafaeezadeh Majid , Akhavan Pari Fadavi
Published: July 2015

A main‐chain N‐heterocyclic carbene (NHC) polymer with N‐dodecyl‐substituted groups was found to be a highly efficient precatalyst for cyanation of various aryl halides by using nontoxic cyanic source [K4Fe(CN)6] under relatively mild reaction conditions. Several aryl iodides, bromides, and activated chlorides were successfully converted to their corresponding benzonitrile derivatives without using additives (such as reducing agents or exogenous organic ligands) in good to excellent yields. Our investigations showed that changing the solvent from DMF to polyethylene glycol (PEG‐200) resulted in dramatic decline of cyanation product formation to the benefit of the Ullmann homocoupling reaction. The catalyst could be reused four and five times with only slight loss of activity in cyanation and the Ullmann coupling, respectively.
Circularly Polarized Luminescence from Simple Organic Molecules
Authors: Sánchez‐Carnerero Esther M. , Agarrabeitia Antonia R. , Moreno Florencio , Maroto Beatriz L. , Muller Gilles , Ortiz María J. , de la Moya Santiago
Published: July 2015

This article aims to show the identity of “circularly polarized luminescent active simple organic molecules” as a new concept in organic chemistry due to the potential interest of these molecules, as availed by the exponentially growing number of research articles related to them. In particular, it describes and highlights the interest and difficulty in developing chiral simple (small and non‐aggregated) organic molecules able to emit left‐ or right‐circularly polarized light efficiently, the efforts realized up to now to reach this challenging objective, and the most significant milestones achieved to date. General guidelines for the preparation of these interesting molecules are also presented.
DNA Photosensitization by an “Insider”: Photophysics and Triplet Energy Transfer of 5‐Methyl‐2‐pyrimidone Deoxyribonucleoside
Authors: Bignon Emmanuelle , Gattuso Hugo , Morell Christophe , Dumont Elise , Monari Antonio
Published: July 2015

The main chromophore of (6‐4) photoproducts, namely, 5‐methyl‐2‐pyrimidone (Pyo), is an artificial noncanonical nucleobase. This chromophore has recently been reported as a potential photosensitizer that induces triplet damage in thymine DNA. In this study, we investigate the spectroscopic properties of the Pyo unit embedded in DNA by means of explicit solvent molecular‐dynamics simulations coupled to time‐dependent DFT and quantum‐mechanics/molecular‐mechanics techniques. Triplet‐state transfer from the Pyo to the thymine unit was monitored in B‐DNA by probing the propensity of this photoactive pyrimidine analogue to induce a Dexter‐type triplet photosensitization and subsequent DNA damage.
Serum Albumin Binding Inhibits Nuclear Uptake of Luminescent Metal‐Complex‐Based DNA Imaging Probes
Authors: Wragg Ashley , Gill Martin R. , McKenzie Luke , Glover Caroline , Mowll Rachel , Weinstein Julia A. , Su Xiaodi , Smythe Carl , Thomas Jim A.
Published: July 2015

The DNA binding and cellular localization properties of a new luminescent heterobimetallic IrIIIRuII tetrapyridophenazine complex are reported. Surprisingly, in standard cell media, in which its tetracationic, isostructural RuIIRuII analogue is localized in the nucleus, the new tricationic complex is poorly taken up by live cells and demonstrates no nuclear staining. Consequent cell‐free studies reveal that the IrIIIRuII complex binds bovine serum albumin, BSA, in Sudlow’s Site I with a similar increase in emission and binding affinity to that observed with DNA. Contrastingly, in serum‐free conditions the complex is rapidly internalized by live cells, where it localizes in cell nuclei and functions as a DNA imaging agent. The absence of serum proteins also greatly alters the cytotoxicity of the complex, where high levels of oncosis/necrosis are observed due to this enhanced uptake. This suggests that simply increasing the lipophilicity of a DNA imaging probe to enhance cellular uptake can be counterproductive as, due to increased binding to serum albumin protein, this strategy can actually disrupt nuclear targeting.
Chemically Modified Graphene: The Influence of Structural Properties on the Assessment of Antioxidant Capacity
Authors: Hui Kai Hwee , Pumera Martin , Bonanni Alessandra
Published: July 2015

Graphene materials obtained by different synthetic routes possess dissimilar amount of defects and surface functionalities, which can influence their electrochemical performance towards the detection of electroactive probes. Oxygen‐containing groups can be either detrimental to the heterogeneous charge transfer or promote favorable interactions between the graphene surface and the analyte of interest, depending on the structure of the latter. Here, we compared three chemically modified graphenes, obtained by various procedures and carrying different amounts of oxygen functionalities, for the detection of standard gallic acid, a compound commonly used as an index of the antioxidant capacity of food and beverages. We found that electrochemically reduced graphene provided the best electrochemical performance in terms of calibration sensitivity, selectivity, and linearity of response. Our findings are important in order to understand the suitability of graphene platforms for the assessment of food quality.
Therapeutic Developments Targeting Toll‐like Receptor‐4‐Mediated Neuroinflammation
Authors: Li Jing , Csakai Adam , Jin Jialin , Zhang Fengchun , Yin Hang
Published: July 2015

Toll‐like receptors (TLRs) have been shown to play an important role in the immune system, which warrants study of their remarkable potential as pharmacological targets. Activation of TLRs requires participation from specific pathogen‐associated molecular patterns (PAMPs) and accessory proteins such as myeloid differentiation protein 2 (MD2), lipopolysaccharide binding protein (LBP), and cluster differentiation antigen 14 (CD14). Assembly of the TLR4–MD2–LPS complex is essential in TLR4 activation. Recent studies have revealed that TLR4 activation is a significant trigger of signal transmission pathways in the nervous system, which could result in chronic pain as well as opioid tolerance and dependence. Researchers of the molecular structure of TLRs and their accessory proteins have opened a door to syntheses of TLRs agonists and antagonists, such as eritoran. Small‐molecule modulators of TLR4, such as MD2‐I and tricyclic antidepressants, offer more promising prospects than peptides, given their convenience in oral administration and lower cost. Herein we mainly discuss the mechanisms and clinical prospects of TLR4 agonists and antagonists.
Synaptic ultrastructure changes in trigeminocervical complex posttrigeminal nerve injury
Authors: Park John , Trinh Van Nancy , Sears‐Kraxberger Ilse , Li Kang‐Wu , Steward Oswald , Luo Z. David
Published: July 2015

Trigeminal nerves collecting sensory information from the orofacial area synapse on second‐order neurons in the dorsal horn of subnucleus caudalis and cervical C1/C2 spinal cord (Vc/C2, or trigeminocervical complex), which is critical for sensory information processing. Injury to the trigeminal nerves may cause maladaptive changes in synaptic connectivity that plays an important role in chronic pain development. Here we examined whether injury to the infraorbital nerve, a branch of the trigeminal nerves, led to synaptic ultrastructural changes when the injured animals have developed neuropathic pain states. Transmission electron microscopy was used to examine synaptic profiles in Vc/C2 at 3 weeks postinjury, corresponding to the time of peak behavioral hypersensitivity following chronic constriction injury to the infraorbital nerve (CCI‐ION). Using established criteria, synaptic profiles were classified as associated with excitatory (R‐), inhibitory (F‐), and primary afferent (C‐) terminals. Each type was counted within the superficial dorsal horn of the Vc/C2 and the means from each rat were compared between sham and injured animals; synaptic contact length was also measured. The overall analysis indicates that rats with orofacial pain states had increased numbers and decreased mean synaptic length of R‐profiles within the Vc/C2 superficial dorsal horn (lamina I) 3 weeks post‐CCI‐ION. Increases in the number of excitatory synapses in the superficial dorsal horn of Vc/C2 could lead to enhanced activation of nociceptive pathways, contributing to the development of orofacial pain states. J. Comp. Neurol. 524:309–322, 2016. © 2015 Wiley Periodicals, Inc.