bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strong Solid‐State Phosphorescence of 1,2‐Telluraplatinacycles Incorporated into Rigid Dibenzobarrelene and Triptycene Skeletons
Authors: Yamaguchi Yuki , Nakata Norio , Ishii Akihiko 
Published: October 2013

AbstractFour‐ and five‐membered 1,2‐telluraplatinacycles incorporated into dibenzobarrelene and triptycene skeletons were synthesized by the reaction of bis(dibenzobarrelenyl) ditelluride and bis(triptycyl) ditelluride, respectively, with [Pt(η2‐norbornene)(PPh3)2] in the presence of PPh3. These complexes emit strong, orange phosphorescence in the solid state at room temperature (λem = 622–676 nm). Ligand‐exchange reactions of a five‐membered telluraplatinacycle with bidentate phosphine ligands gave a series of derivatives that emitted a range of colors (blue to orange, λem = 507–596 nm) with high emission quantum yields (max. ΦF = 0.93) in the solid state at room temperature, for which vapoluminescence was observed.
Synthesis of a Cn–Cn+6 Building Block Common to Important Polyol,Polyene Antibiotics from a Divinylcarbinol by a Desymmetrizing Sharpless Epoxidation
Authors: Nachbauer Luc , Brückner Reinhard 
Published: October 2013

AbstractA stereocontrolled synthesis of the enantiomerically pure epoxide 7b from propargyl ether 15 has been realized in 15 steps. Epoxide 7b represents a building block for the “eastern” moieties of the title compounds. Key steps in our approach were a desymmetrizing Sharpless epoxidation (→ anti,cis‐16), the selective processing of the bis‐enolate of the bis(tert‐butyl alkoxyacetate) 11 through a diastereoselective [2,3]‐Wittig rearrangement (→ syn,syn‐9), and a stereo‐ and chemoselective iodolactonization (→ 35). The CO2H groups of dicarboxylic acid 37 were differentiated in a one‐pot bis‐oxidation reaction. The latter entailed the novel transformation of HO2CCH2‐O‐alkyl into AcOCH2‐O‐alkyl.
Stereocontrolled Synthesis of a Cn–Cn+6Building Block for the Unnatural Enantiomers of Important Polyol,Polyene Antibiotics from an Epoxy Alcohol by a Reduction/Conjugate Addition/Hydroxylation Sequence
Authors: Kramer Rainer , Brückner Reinhard 
Published: October 2013

AbstractEpoxy alcoholanti‐10, derived from a desymmetrizing Sharpless epoxidation (up to 97 %ee) of divinylcarbinol9, provided the unsaturated 1,3‐diolsyn‐11upon treatment with RedAl®;syn‐11was converted into the α,β‐unsaturated esters (E)‐ or (Z)‐7bin three steps. Cu‐promoted 1,4‐addition of vinylmagnesium halides to the (E)‐ester proceeded with diastereoselectivities of up to 91 % and Cu‐catalyzed 1,4‐additions with diastereoselectivities of up to 82 %. The potassium enolate of the major vinylation productsyn‐22bwas hydroxylated by the Davis oxaziridine with perfect but unprecedented diastereoselectivity. The resulting hydroxy ester,α,βsyn,β,γsyn‐32, furnished the “eastern moiety” building block6of the title compounds in three steps.
Gold‐Catalyzed Cascade Oxidative Cyclization and Arylation of Allenoates
Authors: Zhang Rui , Xu Qin , Chen Kai , Gu Peng , Shi Min 
Published: October 2013

AbstractAn AuI/AuIII catalytic system was found to be effective for the cascade oxidative arylation and cyclization of allenoates with arylboronic acids to give the corresponding cyclic adducts in moderate yields. This reaction system constitutes a new method for the synthesis of β‐aryl‐γ‐butenolides under mild conditions. Based on the previous mechanistic studies, a proposed AuI/AuIII redox catalytic cycle has been outlined.
Fluorocarbon and Hydrocarbon N‐Heterocyclic (C5–C7) Difluorooxymethylene‐Bridged Liquid Crystals
Authors: Chen Hongren , Liu Peilian , Li Huijuan , Zhang Hong , Daniel Stelck , Zeng Zhuo 
Published: October 2013

AbstractA series of new fluorocarbon and hydrocarbon N‐heterocyclic (C5–C7) difluorooxymethylene‐bridged liquid crystals have been prepared. The impact of ring (C5–C7) as end group was investigated. Compounds with terminal N‐heterocyclic 5‐ or 6‐membered rings such as 3,4‐difluoropyrrole, pyrrolidine, or pyridine, exhibited nematic phases (N). Whereas the terminal 3,3,4,4‐tetrafluoropyrrolidine and 3,3,4,4,5,5‐hexafluoropiperidine derivatives exhibited smectic C and B phases; the mesomorphic behavior weakened with increasing ring size. These new compounds also exhibited promising physicochemical and electro‐optical properties. Modification of the ring size with different length alkyl groups and variation of the chains from alkyl to polyfluoroalkyl markedly changed the properties of these compounds. It is possible that these N‐heterocycles (C5–C7) could replace fluorobenzene as terminal groups to form valuable difluorooxymethylene‐bridged liquid crystals. Compounds with 3,4‐difluoropyrrole as terminal group showed strongly positive dielectric anisotropy (Δϵ), moderate birefringence (Δn), and relatively low viscosity (γ1), thus meeting the criterion for high‐performance liquid‐crystalline materials.
Stereoselective Synthesis of a Bicyclic Norsesquiterpene Backbone – A Possible Route to Nardosinane Derivatives
Authors: Selaïmia‐Ferdjani Ouassila , Kar Anirban , Chavan Sambhaji P. , Horeau Maxime , Viault Guillaume , Pouessel Jacky , Guillory Xavier , Blot Virginie , Tessier Arnaud , Planchat Aurelien , Jacquemin Denis , Dubreuil Didier , Pipelier Muriel 
Published: October 2013

AbstractWe have developed an efficient diastereoselective synthetic route towards a nardosinane sesquiterpene scaffold. The strategy used a key bicyclic diene intermediate 11a, and allowed access to valuable polyoxygenated sesquiterpenes 21 and 22, which may be regarded as analogues of the natural sesquiterpenes laevinol B and fulvol acetate, respectively.
Iridium‐Catalyzed Direct Dehydroxylation of Alcohols
Authors: Huang Jian‐Lin , Dai Xi‐Jie , Li Chao‐Jun 
Published: October 2013

AbstractIridium‐catalyzed direct dehydroxylation of alcohols with hydrazine was developed through a combination of the oxidation of alcohols and the Wolff–Kishner reduction. This protocol is simple to perform and highly efficient for a series of primary, benzylic and allylic alcohols.
Chitosan/Ionic Liquid Composite Electrode for Electrochemical Monitoring of the Surface‐Confined Interaction Between Mitomycin C and DNA
Authors: Eksin Ece , Muti Mihrican , Erdem Arzum 
Published: October 2013

AbstractIn the present study a chitosan/ionic liquid modified pencil graphite electrode (CHIT‐IL‐PGEs) was developed for the first time for enhanced electrochemical monitoring of nucleic acid, and the interaction of the anticancer drug Mitomycin C (MC) and calf thymus double stranded DNA (dsDNA) by measuring the oxidation signals of MC and guanine in the same voltammetric scale. Differential pulse voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to evaluate the performance of the CHIT‐IL based biosensor on electrochemical monitoring of DNA, and drug‐DNA interaction. The experimental parameters, IL, dsDNA and MC concentration and the interaction time were then optimized.
Direct Electrodeposition of Graphene‐Gold Nanocomposite Films for Ultrasensitive Voltammetric Determination of Mercury(II)
Authors: Ding Liang , Liu Yuping , Zhai Jianping , Bond Alan M. , Zhang Jie 
Published: October 2013

AbstractGraphene‐gold nanocomposite (rGO‐Au) modified glassy carbon electrodes (GCE) have been fabricated by a one‐step electrodeposition method. The nanocomposites were characterized by scanning electron microscopy, energy dispersive X‐ray spectroscopy, Raman spectra as well as electrochemical methods, and were utilized for mercury(II) detection via anodic stripping voltammetry. The peak stripping current was linearly dependent on the concentration of Hg(II) over the range of 1.0 to 150.0 nM and high selectivity and sensitivity (limit of detection 0.6 nM) and excellent stability/reusability were achieved. The applicability to environmental samples was successfully demonstrated by the direct determination of Hg(II) in tap water samples with minimal sample pretreatment.
The Influence of Graphene on the Electrical Communication Through Organic Layers on Graphite and Gold Electrodes
Authors: Zong Xidan , Kong Na , Liu Jingquan , Yang Wenrong , Cao Mengmei , Gooding J. Justin 
Published: October 2013

AbstractThe influence of graphene on the electrical communication through organic layers fabricated on graphite and gold electrodes is investigated. These layers were prepared by in situ reductive adsorption of 4‐aminobenzoic acid in the presence of NaNO2 and HCl to have surface bound carboxylic acid functionalities, followed by covalent attachment of 1‐aminopyrene via an amide coupling reaction to have surface bound pyrene groups for graphene immobilization via noncovalent ππ stacking interaction. The coverage of the layers created via reductive adsorption on graphite electrodes was found to be much higher than that on gold electrodes. It was revealed that graphene significantly enhances the electrical communication through the layers on graphite electrodes but on gold electrodes the enhancement effect through the layers was only minor. However, when gold electrodes were modified with a self‐assembled monolayer (SAM) of propanethiol the subsequent immobilization of graphene resulted in a significant enhancement of the electrical communication. It is also found that immobilization of graphene could affect the electron transfer between the redox probe, pyrene and the underlying electrodes. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize the graphene sheets. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and X‐ray photoelectron spectroscopy (XPS) were also used to characterize the stepwise modified electrodes.
Carbon Black‐Modified Electrodes as Sensitive Tools for the Electrochemical Detection of Nitrite and Nitrate
Authors: Malha Seif Islam Rabie , Mandli Jihane , Ourari Ali , Amine Aziz 
Published: October 2013

AbstractBoth screen‐printed electrodes modified with a dispersion of carbon black (CB) and solid paste electrodes prepared using a nanostructured CB were developed and characterized. Indeed, increasing the peak currents and/or their shifting to negative potentials were observed, exhibiting efficient electrocatalytic activity towards nitrite oxidation with high sensitivity and low detection limit. Solid carbon paste electrodes (SCPEs) and solid carbon black paste electrodes (SCBPEs) were challenged in amperometric mode with nitrite since detection limit reached is 65 and 5 nM respectively. Nitrate was first reduced to nitrite in reductor column, then detected on SCBPEs. Nitrate and nitrite were determined in real samples.
Ultra Flexible Paper Based Electrochemical Sensors: Effect of Mechanical Contortion upon Electrochemical Performance
Authors: Foster Christopher W. , Metters Jonathan P. , Banks Craig E. 
Published: October 2013

AbstractThe influence of mechanical contortion upon the electrochemical performance of screen‐printed graphite paper‐based electroanalytical sensing platforms is evaluated and contrasted with traditionally employed polymeric based screen‐printed graphite sensors. Such a situation of implementation can be envisaged for the potential sensing of analytes on the skin where such sensors are based, for example in clothing where mechanical contortion, viz, bending will occur, and as such, its effect upon electrochemical sensors is of both fundamental and applied importance. The effect of mechanical contortion or stress upon electrochemical behaviour and performance is of screen printed sensors is explored. Comparisons are made between both paper‐ and polymeric‐ based sensing platforms that are evaluated towards the sensing of the well characterised electrochemical probes potassium ferrocyanide(II), hexaammine‐ruthenium(III) chloride and nicotinamide adenine dinucleotide (NADH). It is determined that the paper‐based sensors offer greater resilience in terms of electrochemical performance after mechanical stress. We gain insights into the role played by both the effect of the time of mechanical contortion and additionally the potentially detrimental effects of repeated contortion are explored. These unique paper‐based sensors hold promise for widespread applications where flexible and ultra‐low cost sensors are required such as applications into medical devices were ultra‐low cost sensors are a pre‐requisite, but also for utilisation within applications which require the implementation of ultra‐flexible electroanalytical sensing platforms such as in the case of wearable sensors, whilst maintaining useful electrochemical performances.
Environmentally Friendly Reduction of Graphene Oxide Using Tyrosine for Nonenzymatic Amperometric H2O2 Detection
Authors: Wang Qi , Li Musen , Szunerits Sabine , Boukherroub Rabah 
Published: October 2013

AbstractHerein, we report on the simultaneous reduction and functionalization of graphene oxide (GO) with environmentally friendly tyrosine through the direct reaction of GO with tyrosine (Tyr) at 100 °C for 24 h. The resultant material (rGO/Tyr) has been characterized using UV‐vis spectrometry, FTIR spectroscopy, X‐ray photoelectron spectroscopy (XPS), and electrochemical measurements. The rGO/Tyr nanomaterial displayed good electrocatalytic activity for the detection of hydrogen peroxide (H2O2) with a wide linear range from 100 µM to 2.1 mM, a detection limit of 80 µM and a sensitivity of 69.07 µA mM−1 cm−2. In addition, the rGO/Tyr electrode showed good selectivity for H2O2 detection in the presence of uric acid, ascorbic acid, dopamine and glucose.
Hydrothermal upgrading of algae paste: Application of 31P‐NMR
Authors: Patel Bhavish , Hellgardt Klaus 
Published: October 2013

Although already proposed in the 1940s, hydrothermal upgrading of biomass, and specifically algae, to produce biocrude has only recently become a much researched topic. Algae are of special interest as they are capable of much higher biomass accumulation rates than terrestrial plants. To understand the transformation of algal biomass into biocrude, this process needs to be scrutinized in as much detail as possible to identify the most appropriate reaction conditions. It is usually not possible to identify individual transformation steps; however, in this article we demonstrate the use of 31P‐NMR to follow the fate of derivatized (2‐chloro‐4,4,5,5‐tetramethyl‐1,3,2‐dioxaphospholane) hydroxyl groups to start understand, which chemical species are involved in the initial degradation steps.Our data show the occurrence of a very fast degradation of acidic OH groups (derived from the hydrolysis of lipids) and aliphatic OH groups (derived from the fast hydrolysis of carbohydrates). The degradation of proteins leads to polyphenols, which appear to be rather stable even over prolonged treatment periods. Small quantities of aromatic compounds are also formed as secondary degradation products through sugar dehydration and cyclization as well as peptide transformation. It appears that additional deoxygenation routes exist as the deoxygenation rate using 31P‐NMR and that determined by elemental analysis differ. The formed oil (biocrude) is compared with typical North Sea oils using simulated distillation and was found to contain a significant high boiling faction, which would require further treatment (e.g., hydrocracking) to shift the boiling range to a more valuable oil composition. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 1002–1012, 2013
Model‐based multi‐metric control of uniaxial shake tables
Authors: Phillips Brian M. , Wierschem Nicholas E. , Spencer B. F. 
Published: October 2013

SUMMARYShake tables provide a direct means by which to evaluate structural performance under earthquake excitation. Because the entire structure is mounted on the base plate and subjected to the ground motion in real time, dynamic effects and rate‐dependent behavior can be accurately represented. Shake table control is not straightforward as the desired signal is an acceleration record, while most actuators operate in displacement feedback for stability. At the same time, the payload is typically large relative to the capacity of the actuator, leading to pronounced control‐structure interaction. Through this interaction, the dynamics of the specimen influence the dynamics of the shake table, which can be problematic when specimens change behavior because of damage or other nonlinearities. Moreover, shake tables are themselves inherently nonlinear, making it difficult to accurately recreate a desired acceleration record over a broad range of amplitudes and frequencies. A model‐based multi‐metric shake table control strategy is proposed to improve tracking of the desired acceleration of a uniaxial shake table, remaining robust to nonlinearities including changes in specimen condition. The proposed strategy is verified for the shake table testing of both linear and nonlinear structures. Copyright © 2013 John Wiley & Sons, Ltd.
Wind erosion on the north‐eastern Tibetan Plateau: constraints from OSL and U‐Th dating of playa salt crust in the Qaidam Basin
Authors: Han Wenxia , Ma Zhibang , Lai Zhongping , Appel Erwin , Fang Xiaomin , Yu Lupeng 
Published: October 2013

ABSTRACTThe arid Qaidam Basin is the largest (~3.88 × 104 km2) basin on the north‐eastern Tibetan Plateau. Wind erosion in the area has been regarded as an important trigger for intra‐basin tectonic balance upheaval, geomorphologic development and as a major supplier of dust to the Chinese Loess Plateau downwind. An initial estimate of the rate of wind erosion (Kapp et al., 2011) based on geological cross‐sections has suggested up to 3.2 × 104 km3 of sediments has been deflated over the past 2.8 Ma, lowering the landscape by an average of 0.29 mm/yr. In this paper we re‐evaluate this estimate by dating surface crusts present on three playas within the basin. Understanding the development of these playas is crucial to assessing the overall role of the wind in shaping the regional landscape because they are typically capped with a thick salt crust which effectively protects them from wind erosion. Optically stimulated luminescence (OSL) and U‐series dating from a pit section and from the top of a deep drill core, together with results from magnetostratigraphy and a climate proxy record correlated to the marine oxygen isotope record, are used here to determine the age of the playa plains and suggest that the salt crusts have an age of c. 0.1 Ma. This young age and the wide distribution of resistant thick salt crusts of the playa plains indicate a much lower degree of wind erosion than previously suggested. The crusts protect the surface from significant surface erosion (including sediment exhumation and unloading) and whilst some wind erosion does occur, it is unlikely to be sufficient to trigger tectonic uplift of the basin or to be a major dust source for the Loess Plateau as previously suggested. Copyright © 2013 John Wiley & Sons, Ltd.
Comparison of the toxicity of fluoridation compounds in the nematode Caenorhabditis elegans
Authors: Rice Julie R. , Boyd Windy A. , Chandra Dave , Smith Marjolein V. , Besten Pamela K. Den , Freedman Jonathan H. 
Published: October 2013

Abstract

Fluorides are commonly added to drinking water in the United States to decrease the incidence of dental caries. Silicofluorides, such as sodium hexafluorosilicate (Na2SiF6) and fluorosilicic acid (H2SiF6), are mainly used for fluoridation, although fluoride salts such as sodium fluoride (NaF) are also used. Interestingly, only the toxicity of NaF has been examined and not that of the more often used silicofluorides. In the present study, the toxicities of NaF, Na2SiF6, and H2SiF6 were compared. The toxicity of these fluorides on the growth, feeding, and reproduction in the alternative toxicological testing organism Caenorhabditis elegans was examined. Exposure to these compounds produced classic concentration–response toxicity profiles. Although the effects of the fluoride compounds varied among the 3 biological endpoints, no differences were found between the 3 compounds, relative to the fluoride ion concentration, in any of the assays. This suggests that silicofluorides have similar toxicity to NaF. Environ Toxicol Chem 2013;33:82–88. © 2013 SETAC
CAD‐based shape optimisation with CFD using a discrete adjoint
Authors: Xu Shenren , Jahn Wolfram , Müller Jens‐Dominik 
Published: October 2013

SUMMARYOne of the major challenges of shape optimisation in practical industrial cases is to generically parametrise the wide range of complex shapes. A novel approach is presented, which takes CAD descriptions as input and produces the optimal shape in CAD form using the control points of the Non‐Uniform Rational B‐Splines (NURBS) boundary representation as design variables. An implementation of the NURBS equations in source allows to include the CAD‐based shape deformation inside the design loop and evaluate its sensitivities efficiently and robustly. In order to maintain or establish the required level of geometric continuity across patch interfaces, geometric constraints are imposed on the control point displacements. The paper discusses the discrete adjoint flow solver used and the computation of the complete sensitivities of the design loop by differentiating all components using automatic differentiation tools. The resulting rich but smooth deformation space is demonstrated on the optimisation of a vehicle climate duct. Copyright © 2013 John Wiley & Sons, Ltd.
A PFSA Composite Membrane with Sulfonic Acid Functionalized TiO2 Nanotubes for Polymer Electrolyte Fuel Cells and Water Electrolysers
Authors: Wu X. , Scott K. 
Published: October 2013

AbstractTitanate nanotubes (TiO2‐NT) were functionalized with sulfonic acid functional groups and characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). Results confirmed that sulfonic acid groups were grafted onto TiO2‐NT with a uniform distribution. When the functionalized titanate nanotube (F‐TiO2‐NT) was incorporated in perfluorosulfonic acid membranes, the membrane conductivity and water uptake were improved. Polymer electrolyte membrane (PEM) fuel cells using 5 wt.% F‐TiO2‐NT incorporated composite membrane exhibited a peak power density of 429 mW cm–2 with non‐humidified O2 at 90 °C, which is about four times higher than that with Nafion 117 membrane at identical conditions. PEMWE with 5 wt.% F‐TiO2‐NT incorporated composite membrane achieved 1,000 mA cm–2 current density at voltages below 1.6 V at 90 °C without back pressurizing.