bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three Roles for the Fluoride Ion in Palladium‐Catalyzed Hiyama Reactions: Transmetalation of [ArPdFL2] by Ar′Si(OR)3
Authors: Amatore Christian , Grimaud Laurence , Le Duc Gaëtan , Jutand Anny 
Published: May 2014

AbstractFrom the kinetic data on the transmetalation/reductive elimination in fluoride‐promoted Hiyama reactions, obtained using electrochemical techniques, it has been established that fluoride ions play three roles. F− reacts with trans‐[ArPdBrL2] (L=PPh3) to form trans‐[ArPdFL2], which reacts with Ar′Si(OMe)3 in the rate‐determining transmetalation, whereas trans‐[ArPdBrL2] does not react with Ar′Si(OMe)3. F− reacts with Ar′Si(OMe)3 to deliver the unreactive silicate Ar′SiF(OMe)3−, thus leading to two antagonistic kinetic effects. In addition, F− catalyzes the reductive elimination from intermediate trans‐[ArPdAr′L2].
Conjugated‐Polyelectrolyte‐Based Polyprodrug: Targeted and Image‐Guided Photodynamic and Chemotherapy with On‐Demand Drug Release upon Irradiation with a Single Light Source
Authors: Yuan Youyong , Liu Jie , Liu Bin 
Published: May 2014

AbstractNanomaterials that combine diagnostic and therapeutic functions within a single nanoplatform are highly desirable for molecular medicine. Herein we report a novel theranostic platform based on a conjugated‐polyelectrolyte (CPE) polyprodrug that contains functionality for image, chemo‐ and photodynamic therapy (PDT), and on‐demand drug release upon irradiation with a single light source. Specifically, the PEGylated CPE serves as a photosensitizer and a carrier, and is covalently conjugated to doxorubicin through a linker that can be cleaved by reactive oxygen species (ROS). Under appropriate light irradiation, the CPE can generate ROS, not only for PDT, but also for on‐demand drug release and chemotherapy. This nanoplatform will offer on‐demand PDT and chemotherapy with drug release triggered by one light switch, which has great potential in cancer treatment.
Electron Transfer and Multi‐Electron Accumulation in ExBox4+
Authors: Dyar Scott M. , Barnes Jonathan C. , Juríček Michal , Stoddart J. Fraser , Co Dick T. , Young Ryan M. , Wasielewski Michael R. 
Published: May 2014

AbstractMolecules capable of accepting and storing multiple electrons are crucial components of artificial photosynthetic systems designed to drive catalysts, such as those used to reduce protons to hydrogen. ExBox4+, a boxlike cyclophane comprising two π‐electron‐poor extended viologen units tethered at both ends by two p‐xylylene linkers, has been shown previously to accept an electron through space from a photoexcited guest. Herein is an investigation of an alternate, through‐bond intramolecular electron‐transfer pathway involving ExBox4+ using a combination of transient absorption and femtosecond stimulated Raman spectroscopy (FSRS). Upon photoexcitation of ExBox4+, an electron is transferred from one of the p‐xylylene linkers to one of the extended viologen units in ca. 240 ps and recombines in ca. 4 ns. A crystal structure of the doubly reduced species ExBox2+ was obtained.
Stress reduction in phase‐separated, cross‐linked networks: Influence of phase structure and kinetics of reaction
Authors: Szczepanski Caroline R. , Stansbury Jeffrey W. 
Published: May 2014

ABSTRACTA mechanism for polymerization shrinkage and stress reduction was developed for heterogeneous networks formed through ambient, photo‐initiated polymerization‐induced phase separation (PIPS). The material system used consists of a bulk homopolymer matrix of triethylene glycol dimethacrylate (TEGDMA) modified with one of three nonreactive, linear prepolymers (poly‐methyl, poly‐ethyl, and poly‐butyl methacrylate). At higher prepolymer loading levels (10–20 wt %), an enhanced reduction in both shrinkage and polymerization stress is observed. The onset of gelation in these materials is delayed to a higher degree of methacrylate conversion (∼15–25%), providing more time for phase structure evolution by thermodynamically driven monomer diffusion between immiscible phases prior to network macro‐gelation. The resulting phase structure was probed by introducing a fluorescently tagged prepolymer into the matrix. The phase structure evolves from a dispersion of prepolymer at low loading levels to a fully co‐continuous heterogeneous network at higher loadings. The bulk modulus in phase‐separated networks is equivalent or greater than that of poly(TEGDMA), despite a reduced polymerization rate and cross‐link density in the prepolymer‐rich domains. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40879.
A sensitive voltammetric sensor based on synergistic effect of graphene–polyaniline hybrid film for quantification of calcium antagonist lercanidipine
Authors: Jain Rajeev , Tiwari Dinesh Chandra , Shrivastava Swati 
Published: May 2014

ABSTRACTA chemically modified sensor based on the synergistic effect of graphene and polyaniline for electrochemical sensing of calcium antagonist lercanidipine (LCP) has been developed. Scanning electron microscopy, electrochemical impedance spectroscopy, square‐wave voltammetry, and cyclic voltammetry were utilized to characterize the morphology and electroanalytical performance of the fabricated sensor. Under optimized conditions, reduction peak current was linear over the wide concentration range from 5 to 125 ng mL−1with correlation coefficient of 0.9998. The limit of detection and the limit of quantification were found to be 1.94 and 5.89 ng mL−1. The developed sensor also exhibited good reproducibility and long‐term stability. In addition, the proposed method was successfully applied to the determination of LCP in pharmaceutical formulation which is proved by recovery studies. Graphene–polyaniline composites are expected to be promising material for biosensing applications because of the ease of fabrication, excellent electrochemical performance, and high electroactive surface area. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2014,131, 40959.
Rapid avatar capture and simulation using commodity depth sensors
Authors: Shapiro Ari , Feng Andrew , Wang Ruizhe , Li Hao , Bolas Mark , Medioni Gerard , Suma Evan 
Published: May 2014

ABSTRACTWe demonstrate a method of acquiring a 3D model of a human using commodity scanning hardware and then controlling that 3D figure in a simulated environment in only a few minutes. The model acquisition requires four static poses taken at 90° angles relative to each other. The 3D model is then given a skeleton and smooth binding information necessary for control and simulation. The 3D models that are captured are suitable for use in applications where recognition and distinction among characters by shape, form, or clothing is important, such as small group or crowd simulations or other socially oriented applications. Because of the speed at which a human figure can be captured and the low hardware requirements, this method can be used to capture, track, and model human figures as their appearances change over time. Copyright © 2014 John Wiley & Sons, Ltd.
Triterpene Saponins from the Roots of Ilex asprella
Authors: Lei Yu , Shi She‐Po , Song Yue‐Lin , Bi Dan , Tu Peng‐Fei 
Published: May 2014

AbstractSix new triterpene saponins, ilexasprellanosides A–F (1–6, resp.), together with eleven known compounds were isolated from the roots of Ilex asprella. The new saponins were characterized as ursa‐12,18‐dien‐28‐oic acid 3‐O‐β‐D‐xylopyranoside (1), 19α‐hydroxyursolic acid 3‐O‐β‐D‐(2′‐O‐acetylxylopyranoside) (2), 19α‐hydroxyursolic acid 3‐O‐β‐D‐glucuronopyranoside (3), 3β,19α‐dihydroxyolean‐12‐en‐23,28‐dioic acid 28‐O‐β‐D‐glucopyranoside (4), 19α‐hydroxyoleanolic acid 3‐O‐β‐D‐(2′‐O‐acetylxylopyranoside) (5), 19α‐hydroxyoleanolic acid 3‐O‐β‐D‐glucuronopyranoside (6). The structures of the new compounds were elucidated by analysis of their spectroscopic data and chemical degradation. Compounds 2, 4, oleanolic acid 3‐O‐β‐D‐glucuronopyranoside, 3‐β‐acetoxy‐28‐hydroxyurs‐12‐ene, and pomolic acid showed significant cytotoxic activities against human tumor cell line A549 (IC50 values of 1.87, 2.51, 1.41, 3.24, and 5.63 μM, resp.).
Two New Avermectin Derivatives from the Beibu Gulf Gorgonian Anthogorgia caerulea
Authors: Gao Chenghai , Wang Yibing , Chen Yinning , He Bijuan , Zhang Rongcan , Xu Mingben , Huang Riming 
Published: May 2014

AbstractTwo new avermectin derivatives, avermectins B1c and B1e (1 and 2, resp.), as well as two known compounds, avermectin B2a (3) and ivermectin A1a (4), were isolated from a Beibu Gulf gorgonian coral, Anthogorgia caerulea. The structures of the new compounds were established by detailed spectroscopic analysis and by comparison with spectral data of related known compounds. Compounds 1–4 showed moderate antifouling activities against the larval settlement of Balanus amphitrite.
Construction of a MoxC/Ni Network Electrode with Low Overpotential for Hydrogen Generation
Authors: Zhang Jian , Meng Xin , Zhao Jianghong , Zhu Zhenping 
Published: May 2014

AbstractThe integration of commercial photovoltaic devices and electrocatalysts has attracted considerable interest to realize the conversion of solar power to renewable hydrogen energy. However, a noble metal electrocatalyst (Pt) is too expensive and rare, which inspires the development of efficient and economical catalytic electrodes. Herein, we have fabricated a 3 D MoxC/Ni network through the carbonization of a polyaniline–Mo7O24 precursor, which was electrochemically deposited on Ni foam in advance. If the 3 D MoxC/Ni network is used as a catalytic electrode for the hydrogen evolution reaction (HER), a low onset potential of approximately 44 mV for driving 1 mA cm−2 of current density and a Tafel slope of approximately 49 mV decade−1 (overpotential η=50–60 mV) are obtained. Moreover, the apparent exchange current density reaches approximately 0.1 mA cm−2. After a long‐term HER test at η=100 mV or 500 CV sweeps, no deactivation is observed. This excellent electrocatalytic performance of the 3 D MoxC/Ni network promotes it as a promising earth‐abundant HER electrode.
Methane Steam Reforming over a Ni/NiAl2O4 Model Catalyst—Kinetics
Authors: Sprung Christoph , Arstad Bjørnar , Olsbye Unni 
Published: May 2014

AbstractThe steam reforming reaction of methane to synthesis gas (CO and H2) was investigated in a very broad steam‐to‐carbon (S/C) ratio range (0.2–7.1) over a Ni/NiAl2O4 catalyst at 843, 858, and 873 K. The dataset includes 179 data points at each temperature giving a detailed insight in the gradual change of kinetic orders in both methane and steam with changing S/C ratios as well as with total reactant partial pressures at differential conversion levels. At low S/C ratios, steam dominates the kinetics with high kinetic orders (low for methane) and vice versa for methane at high S/C ratios. The extent of the water gas shift reaction was assessed by 13CO2 co‐feed experiments and thermodynamic modelling and found to be not in equilibrium. A change in the kinetic isotope effect (i.e., inverse and normal), as well as the apparent activation energy, was observed depending on the applied S/C ratios. The experimental data were satisfactorily described by a Langmuir–Hinshelwood expression.
Epoxidation of Olefins Catalyzed by a Molecular Iron N‐Heterocyclic Carbene Complex: Influence of Reaction Parameters on the Catalytic Activity
Authors: Kück Jens W. , Raba Andreas , Markovits Iulius I. E. , Cokoja Mirza , Kühn Fritz E. 
Published: May 2014

AbstractThe catalytic epoxidation of olefins by an iron(II) complex bearing a tetradentate bis(pyridyl‐N‐heterocyclic carbene) ligand was investigated. This is the first example of the use of an organometallic iron compound (i.e., with a FeC bond) as an olefin epoxidation catalyst. The catalyst system, used without additives, showed good epoxide yields and selectivity for various olefins after a reaction time of 5 min. It was found that the epoxide yield strongly depended on the amount of the peroxide used and its nature and noticeably increased at lower temperatures.
The Primary Steps in Excited‐State Hydrogen Transfer: The Phototautomerization of o‐Nitrobenzyl Derivatives
Authors: Šolomek Tomáš , Bochet Christian G. , Bally Thomas 
Published: May 2014

AbstractThe quantum yield for the release of leaving groups from o‐nitrobenzyl “caged” compounds varies greatly with the nature of these leaving groups, for reasons that have never been well understood. We found that the barriers for the primary hydrogen‐atom transfer step and the efficient nonradiative processes on the excited singlet and triplet surfaces determine the quantum yields. The excited‐state barriers decrease when the exothermicity of the photoreaction increases, in accord with Bell–Evans–Polanyi principle, a tool that has never been applied to a nonadiabatic photoreaction. We further introduce a simple ground‐state predictor, the radical‐stabilization energy, which correlates with the computed excited‐state barriers and reaction energies, and that might be used to design new and more efficient photochemical processes.
Analysis of Dopant Atom Distribution and Quantification of Oxygen Vacancies on Individual Gd‐Doped CeO2 Nanocrystals
Authors: Stroppa Daniel G. , Dalmaschio Cleocir J. , Houben Lothar , Barthel Juri , Montoro Luciano A. , Leite Edson R. , Ramirez Antonio J. 
Published: May 2014

AbstractThis work reports the analysis of the distribution of Gd atoms and the quantification of O vacancies applied to individual CeO2 and Gd‐doped CeO2 nanocrystals by electron energy‐loss spectroscopy. The concentration of O vacancies measured on the undoped system (6.3±2.6 %) matches the expected value given the typical Ce3+ content previously reported for CeO2 nanoparticles. The doped nanoparticles have an uneven distribution of dopant atoms and an atypical amount of O vacant sites (37.7±4.1 %). The measured decrease of the O content induced by Gd doping cannot be explained solely by the charge balance including Ce3+ and Gd3+ ions.
Dendrimeric β‐Cyclodextrin/GdIII Chelate Supramolecular Host–Guest Adducts as High‐Relaxivity MRI Probes
Authors: Martinelli Jonathan , Thangavel Kalaivani , Tei Lorenzo , Botta Mauro 
Published: May 2014

AbstractWe have synthesized a new macromolecular architecture, (PAMAM)‐CD8, which consists of eight β‐cyclodextrin units (β‐CD) attached to a generation 1 poly(amidoamine) (PAMAM) dendrimer through a disulfide bond, which can be cleaved under reducing conditions. This system shows a pronounced hosting capability towards GdIII chelates functionalized with hydrophobic groups, thus leading to well‐defined supramolecular adducts. 1H NMR relaxometric investigations were carried out to follow the formation of adducts with three GdIII chelates based on the ligand architectures of 6‐amino‐6‐methylperhydro‐1,4‐diazepinetetraacetic acid (AAZTA) or 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) suitably functionalized with benzyl or adamantyl (Ad) pendant groups. In particular, the ditopic complex composed of two AAZTA chelating units connected to a central aromatic ring that bears an adamantyl group showed a strong affinity (ca. 106 M−1) for the CD units of the dendrimer, which is two orders of magnitude higher than toward human serum albumin (HSA). Remarkable relaxivity enhancements (i.e., up to 71 % at 1 T and 25 °C) were observed upon the formation of the macromolecular host–guest adducts due to a decrease in the molecular tumbling rate and fast water‐exchange. Reduction experiments and competition studies between the paramagnetic dendrimer and HSA were carried out by relaxometric techniques. The results show that the metal complexes are not displaced by the protein, thus suggesting that this novel macromolecular probe is potentially suitable for applications in vivo.
Synthesis of Chiral Exocyclic Amines by Asymmetric Hydrogenation of Aromatic Quinolin‐3‐amines
Authors: Cai Xian‐Feng , Guo Ran‐Ning , Chen Mu‐Wang , Shi Lei , Zhou Yong‐Gui 
Published: May 2014

AbstractAsymmetric hydrogenation of aromatic quinolin‐3‐amines was successfully developed with up to 94 % enantiomeric excess (ee). Introduction of the phthaloyl moiety to the amino group is crucial to eliminate the inhibition effect caused by the substrate and product, to activate the aromatic ring, and to improve the diastereoselectivity. This new methodology provides direct and facile access to chiral exocyclic amines. Notably, this report is the first on the highly enantioselective hydrogenation of aromatic amines.
Palladium‐Catalyzed Oxidative Carbocyclization–Carbonylation of Allenynes and Enallenes
Authors: Volla Chandra M. R. , Mazuela Javier , Bäckvall Jan‐E. 
Published: May 2014

AbstractA highly efficient oxidative carbocyclization–carbonylation reaction cascade of allenynes and enallenes has been developed using a PdII salt in low catalytic amounts under ambient temperature and pressure (1 atm of carbon monoxide). The use of DMSO as an additive was found to be important for an efficient reaction. A wide range of alcohols as trapping reagents were used to give the corresponding esters in good yields.
Kinetic Modeling of α‐Hydrogen Abstractions from Unsaturated and Saturated Oxygenate Compounds by Carbon‐Centered Radicals
Authors: Paraskevas Paschalis D. , Sabbe Maarten K. , Reyniers Marie‐Françoise , Papayannakos Nikos , Marin Guy B. 
Published: May 2014

AbstractHydrogen abstractions are important elementary reactions in a variety of reacting media at high temperatures in which oxygenates and hydrocarbon radicals are present. Accurate kinetic data are obtained from CBS‐QB3 ab initio (AI) calculations by using conventional transition‐state theory within the high‐pressure limit, including corrections for hindered rotation and tunneling. From the obtained results, a group‐additive (GA) model is developed that allows the Arrhenius parameters and rate coefficients for abstraction of the α‐hydrogen from a wide range of oxygenate compounds to be predicted at temperatures ranging from 300 to 1500 K. From a training set of 60 hydrogen abstractions from oxygenates by carbon‐centered radicals, 15 GA values (ΔGAVos) are obtained for both the forward and reverse reactions. Among them, four ΔGAVos refer to primary contributions, and the remaining 11 ΔGAVos refer to secondary ones. The accuracy of the model is further improved by introducing seven corrections for cross‐resonance stabilization of the transition state from an additional set of 43 reactions. The determined ΔGAVos are validated upon a test set of AI data for 17 reactions. The mean absolute deviation of the pre‐exponential factors (log A) and activation energies (Ea) for the forward reaction at 300 K are 0.238 log(m3 mol−1 s−1) and 1.5 kJ mol−1, respectively, whereas the mean factor of deviation <ρ> between the GA‐predicted and the AI‐calculated rate coefficients is 1.6. In comparison with a compilation of 33 experimental rate coefficients, the <ρ> between the GA‐predicted values and these experimental values is only 2.2. Hence, the constructed GA model can be reliably used in the prediction of the kinetics of α‐hydrogen‐abstraction reactions between a broad range of oxygenates and oxygenate radicals.
Flavylium Network of Chemical Reactions in Confined Media: Modulation of 3′,4′,7‐Trihydroxyflavilium Reactions by Host–Guest Interactions with Cucurbit[7]uril
Authors: Basílio Nuno , Pina Fernando 
Published: May 2014

AbstractIn moderately acidic aqueous solutions, flavylium compounds undergo a pH‐, and in some cases, light‐dependent array of reversible chemical reactions. This network can be described as a single acid–base reaction involving a flavylium cation (acidic form) and a mixture of basic forms (quinoidal base, hemiketal and cis and trans chalcones). The apparent pK′a of the system and the relative mole fractions of the basic forms can be modulated by the interaction with cucurbit[7]uril. The system is studied by using 1H NMR spectroscopy, UV/Vis spectroscopy, flash photolysis, and steady‐state irradiation. Of all the network species, the flavylium cation possesses the highest affinity for cucurbit[7]uril. The rate of interconversion between flavylium cation and the basic species (where trans‐chalcone is dominant) is approximately nine times lower inside the cucurbit[7]uril.
Growth of Fe3O4 Nanorod Arrays on Graphene Sheets for Application in Electromagnetic Absorption Fields
Authors: Zhang Huanming , Zhu Chunling , Chen Yujin , Gao Hong 
Published: May 2014

AbstractA facial strategy is developed to fabricate a three‐dimensional (3D) Fe3O4 nanorod array/graphene architecture, in which Fe3O4 nanorods with a length and diameter of about 600 and 100 nm, respectively, are grown on both surfaces of the graphene sheets. The measured electromagnetic parameters show that the 3D architecture exhibits excellent electromagnetic wave‐absorption properties, that is, more than 99 % of electromagnetic wave energy can be attenuated by the 3D architecture if it is added in only 20 wt % of the paraffin matrix, as the thickness of the absorber is in the range from 2.38 to 5.00 mm. The analysis of the electromagnetic (EM) absorption mechanism reveals that the excellent EM absorption properties are related to the special 3D architecture, and therefore, the construction of graphene‐based 3D heteronanostructures is effective in obtaining lightweight EM absorbers with strong absorption properties.
PD‐L1 gene polymorphisms and low serum level of PD‐L1 protein are associated to type 1 diabetes in Chile
Authors: Pizarro Carolina , García‐Díaz Diego F. , Codner Ethel , Salas‐Pérez Francisca , Carrasco Elena , Pérez‐Bravo Francisco 
Published: May 2014

AbstractIntroductionType 1 diabetes (T1D) has a complex etiology in which genetic and environmental factors are involved, whose interactions have not yet been completely clarified. In this context, the role in PD‐1 pathway and its ligands 1 and 2 (PD‐L1 and PD‐L2) have been proposed as candidates in several autoimmune diseases. The aim of this work was to determine the allele and haplotype frequency of six gene polymorphisms of PD‐ligands (PD‐L1 and PD‐L2) in Chilean T1D patients and their effect on serum levels of PD‐L1 and autoantibody profile (GAD65 and IA2).MethodsThis study cohort comprised 205 T1D patients and 205 normal children. We performed genotypic analysis of PD‐L1 and PD‐L2 genes by TaqMan method. Determination of anti‐GAD65 and anti‐IA‐2 autoantibodies was performed by ELISA. The PD‐L1 serum levels were measured.ResultsThe allelic distribution of PD‐L1 variants (rs2297137 and rs4143815) showed differences between T1D patients and controls (p = 0.035 and p = 0.022, respectively). No differences were detected among the PD‐L2 polymorphisms, and only the rs16923189 showed genetic variation. T1D patients showed decreased serum levels of PD‐L1 compared to controls: 1.42 [0.23–7.45] ng/mL versus 3.35 [0.49–5.89] ng/mL (p < 0.025). In addition, the CGG haplotype in PD‐L1 associated with T1D (constructed from rs822342, rs2297137 and rs4143815 polymorphisms) showed an OR = 1.44 [1.08 to 1.93]. Finally, no association of these genetic variants was observed with serum concentrations of PD ligands or auto‐antibody profile, although a correlation between PD‐L1 ligand serum concentration and the age at disease onset was detected.ConclusionTwo polymorphism of PD‐L1 are presented in different allelic variants between T1D and healthy subjects, also PDL‐1 serum levels are significantly lowered in diabetics patients. Moreover, the age of onset of the disease determine differences between serum ligand levels in diabetics, being lower in younger. These results points to a possible establishment of PDL‐1 as a genetic and biochemical marker for T1D onset, at least in Chilean population. Copyright © 2014 John Wiley & Sons, Ltd.