bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanistic Studies of Hoveyda–Grubbs Metathesis Catalysts Bearing S‐, Br‐, I‐, and N‐coordinating Naphthalene Ligands
Authors: Grudzień Krzysztof , Żukowska Karolina , Malińska Maura , Woźniak Krzysztof , Barbasiewicz Michał 
Published: February 2014

AbstractDerivatives of the Hoveyda–Grubbs complex bearing S‐, Br‐, I‐, and N‐coordinating naphthalene ligands were synthesized and characterized with NMR and X‐ray studies. Depending on the arrangement of the coordinating sites on the naphthalene core, the isomeric catalysts differ in activity in model metathesis reactions. In particular, complexes with the RuCH bond adjacent to the second aromatic ring of the ligand suffer from difficulties experienced on their preparation and initiation. The behavior most probably derives from steric hindrance around the double bond and repulsive intraligand interactions, which result in abnormal chemical shifts of benzylidene protons observed with 1H NMR. Furthermore EXSY studies revealed that the halogen‐chelated ruthenium complexes display an equilibrium, in which major cis‐Cl2 structures are accompanied with small amounts of isomeric forms. In general, contents of the minor forms, measured at 80 °C, correlate with the observed activity trends of the catalysts, although some exceptions complicate the mechanistic picture. We assume that for the family of halogen‐chelated metathesis catalysts the initiation mechanism starts with the cis‐Cl2⇌trans‐Cl2 isomerization, although further steps may become rate‐limiting for selected systems.
Preparation and Unique Electrical Behaviors of Monodispersed Hybrid Nanorattles of Metal Nanocores with Hairy Electroactive Polymer Shells
Authors: Cai Tao , Zhang Bin , Chen Yu , Wang Cheng , Zhu Chun Xiang , Neoh Koon‐Gee , Kang En‐Tang 
Published: February 2014

AbstractA versatile template‐assisted strategy for the preparation of monodispersed rattle‐type hybrid nanospheres, encapsulating a movable Au nanocore in the hollow cavity of a hairy electroactive polymer shell (Au@air@PTEMA‐g‐P3HT hybrid nanorattles; PTEMA: poly(2‐(thiophen‐3‐yl)ethyl methacrylate; P3HT: poly(3‐hexylthiophene), was reported. The Au@silica core‐shell nanoparticles, prepared by the modified Stöber sol–gel process on Au nanoparticle seeds, were used as templates for the synthesis of Au@silica@PTEMA core‐double shell nanospheres. Subsequent oxidative graft polymerization of 3‐hexylthiophene from the exterior surface of the Au@silica@PTEMA core‐double shell nanospheres allowed the tailoring of surface functionality with electroactive P3HT brushes (Au@silica@PTEMA‐g‐P3HT nanospheres). The Au@air@ PTEMA‐g‐P3HT hybrid nanorattles were obtained after etching of the silica interlayer by HF. The as‐prepared nanorattles were dispersed into an electrically insulating polystyrene matrix and for the first time used to fabricate nonvolatile memory devices. As a result, unique electrical behaviors, including insulator behavior, write‐once‐read‐many‐times and rewritable memory effects, and conductor behavior as well, were observed in the Al/Au@air@PTEMA‐g‐P3HT+PS/ITO (ITO: indium‐tin oxide) sandwich thin‐film devices.
Alkyne/Alkene/Allene‐Induced Disproportionation of Cationic Gold(I) Catalyst
Authors: Kumar Manish , Jasinski Jacek , Hammond Gerald B. , Xu Bo 
Published: February 2014

AbstractThe first detailed experimental study of the deactivation of cationic gold was conducted, and the influence of each component in the reaction system (substrate, counterion, solvent) on the decay process was examined. It was found that a substrate (alkyne/allene/alkene)‐induced disproportionation of gold(I) may play a key role in the decay process. Our mechanism is supported by kinetic, XPS, voltammetry studies, and high‐resolution ESI‐MS data.
Supramolecular Polymers Self‐Assembled from trans‐Bis(pyridine) Dichloropalladium(II) and Platinum(II) Complexes
Authors: Chen Mingming , Wei Chengsha , Tao Jiaojiao , Wu Xibo , Huang Ningdong , Zhang Guobin , Li Liangbin 
Published: February 2014

AbstractTwo structurally similar trans‐bis(pyridine) dichloropalladium(II)‐ and platinum(II)‐type complexes were synthesized and characterized. They both self‐assemble in n‐hexane to form viscous fluids at lower concentrations, but form metallogels at sufficient concentrations. The viscous solutions were studied by capillary viscosity measurements and UV/Vis absorption spectra monitored during the disassembly process indicated that a metallophilic interaction was involved in the supramolecular polymerization process. For the two supramolecular assemblies, uncommon continuous porous networks were observed by using SEM and TEM revealed that they were built from nanofibers that fused and crosslinked with the increase of concentration. The xerogels of the palladium and platinum complexes were carefully studied by using synchrotron radiation WAXD and EXAFS. The WAXD data show close stacking distances driven by π–π and metal–metal interactions and an evident dimer structure for the platinum complex was found. The coordination bond lengths were extracted from fitting of the EXAFS data. Moreover, close PtII–PtII (PdII–PdII) and PtCl (PdCl) interactions proposed from DFT calculations in the reported oligo(phenylene ethynylene) (OPE)‐based palladium(II) pyridyl supramolecular polymers were also confirmed by using EXAFS. The PtII–PtII interaction is more feasible for supramolecular interaction than the PdII–PdII interaction in our simple case.
Transformation of a Cp*–Iridium(III) Precatalyst for Water Oxidation when Exposed to Oxidative Stress
Authors: Zuccaccia Cristiano , Bellachioma Gianfranco , Bortolini Olga , Bucci Alberto , Savini Arianna , Macchioni Alceo 
Published: February 2014

AbstractThe reaction of [Cp*Ir(bzpy)NO3] (1; bzpy=2‐benzoylpyridine, Cp*=pentamethylcyclopentadienyl anion), a competent water‐oxidation catalyst, with several oxidants (H2O2, NaIO4, cerium ammonium nitrate (CAN)) was studied to intercept and characterize possible intermediates of the oxidative transformation. NMR spectroscopy and ESI‐MS techniques provided evidence for the formation of many species that all had the intact Ir–bzpy moiety and a gradually more oxidized Cp* ligand. Initially, an oxygen atom is trapped in between two carbon atoms of Cp* and iridium, which gives an oxygen–Ir coordinated epoxide, whereas the remaining three carbon atoms of Cp* are involved in a η3 interaction with iridium (2 a). Formal addition of H2O to 2 a or H2O2 to 1 leads to 2 b, in which a double MeCOH functionalization of Cp* is present with one MeCOH engaged in an interaction with iridium. The structure of 2 b was unambiguously determined in the solid state and in solution by X‐ray single‐crystal diffractometry and advanced NMR spectroscopic techniques, respectively. Further oxidation led to the opening of Cp* and transformation of the diol into a diketone with one carbonyl coordinated at the metal (2 c). A η3 interaction between the three non‐oxygenated carbons of “ex‐Cp*” and iridium is also present in both 2 b and 2 c. Isolated 2 b and mixtures of 2 a–c species were tested in water‐oxidation catalysis by using CAN as sacrificial oxidant. They showed substantially the same activity than 1 (turnover frequency values ranged from 9 to 14 min−1).
Identification and Synthesis of Macrolide Pheromones of the Grain Beetle Oryzaephilus Surinamensis and the Frog Spinomantis Aglavei
Authors: Hötling Susann , Haberlag Birte , Tamm Matthias , Collatz Jana , Mack Patrick , Steidle Johannes L. M. , Vences Miguel , Schulz Stefan 
Published: February 2014

AbstractMacrolide lactones, the so called cucujolides derived from unsaturated fatty acids, are aggregation pheromones of cucujid grain beetles. Thirty years ago, Oehlschlarger et al. showed that (3Z,6Z)‐dodeca‐3,6‐dien‐11‐olide (4) and the respective 12‐olide (7) attract the sawtoothed grain beetle Oryzaephilus surinamensis, whereas (5Z,8Z,13R)‐tetradeca‐5,8‐dien‐13‐olide (5) increases the response synergistically. The frass of this beetle is attractive for its parasitoid Cephalonomia tarsalis, which potentially can be used for pest control. A GC/MS analysis of attractive frass showed the presence of 5, together with an unknown isomer. Cucujolide V was tentatively identified also in the femoral glands, pheromone‐releasing structures, of the Madagascan mantelline frog Spinomantis aglavei. Therefore, a new route to synthesize doubly unsaturated macrolides allowing the flexible attachment of the side chain was developed. A straightforward method to obtain Z configured macrolides involves ring‐closing alkyne metathesis (RCAM) followed by Lindlar‐catalyzed hydrogenation. This methodology was extended to homoconjugated diene macrolides by using RCAM after introduction of one Z configured double bond in the precursor by Wittig reaction. A tungsten benzylidyne complex was used as the catalyst in the RCAM reaction, which afforded the products in high yield at room temperature. With the synthetic material at hand, the unknown isomer was identified as the new natural product (5Z,8Z,12R)‐tetradeca‐5,8‐dien‐12‐olide, cucujolide X (8). Furthermore, the route also allowed the synthesis of cucujolide V in good yield. The natural products were identified by the synthesis of enantiomerically pure or enriched material and gas chromatography on chiral phases. The new macrolide (R)‐8 proved to be biologically active, attracting female O. surinamensis, but no males. The synthetic material allowed the identification of (R)‐5 in both the beetle and the frog.
One‐Pot Synthesis of Pd‐Loaded SnO2 Yolk–Shell Nanostructures for Ultraselective Methyl Benzene Sensors
Authors: Hong Young Jun , Yoon Ji‐Wook , Lee Jong‐Heun , Kang Yun Chan 
Published: February 2014

AbstractA continuous, single‐step, and large‐scale preparation of Pd‐catalyst‐loaded SnO2 yolk–shell spheres is demonstrated. These nanostructures show an unusually high response and selectivity to methyl benzenes, such as xylene and toluene, with very low cross‐responses to various interfering gases, making them suitable for precise monitoring of indoor air quality.
Azocinoindole Synthesis by a Gold(I)‐Catalyzed Ring Expansion of 2‐Propargyl‐β‐Tetrahydrocarboline
Authors: Zhang Lei , Chang Lina , Hu Hongwen , Wang Huaqin , Yao Zhu‐Jun , Wang Shaozhong 
Published: February 2014

AbstractA new methodology taking advantage of gold(I)‐catalyzed ring expansion has been developed to assemble tricyclic 1H‐azocino[5,4‐b]indoles from 2‐propargyl‐β‐tetrahydrocarbolines. The azocinoindoles were obtained in moderate to excellent yields; the structure of which was established by X‐ray crystallographic analysis. A mechanism involving regioselective intramolecular hydroarylation, [1,2]‐alkenyl migration and carbon–carbon bond‐fragmentation was proposed.
A Versatile and Stereocontrolled Total Synthesis of Dihydroxylated Docosatrienes Containing a Conjugated E,E,Z‐Triene
Authors: Dayaker Gandrath , Durand Thierry , Balas Laurence 
Published: February 2014

AbstractA versatile strategy featuring a Colvin rearrangement, hydrozirconation, a Sonogashira cross‐coupling reaction and a Z‐selective Wittig olefination, was successfully developed for the construction of a conjugated E,E,Z‐triene subunit, flanked on both sides by two Z‐allylic hydroxyl groups. This chemical pattern is found in many endogenous lipid metabolites such as maresin 1 (MaR1), neuroprotectin D1 (NPD1), and its aspirin triggered‐isomer AT‐NPD1, which not only counter‐regulate inflammation but also actively orchestrate (at nanomolar doses) the resolution and termination program of acute inflammation while promoting wound healing, return to homeostasis and neuroprotection. Unlike previous approaches, the advantages of the present strategy are obvious, as it allows us to modify the nonpolar tail, the carboxylated head or both ends of the molecule without repeating the whole synthetic sequence (about 26–34 steps according to the literature). Thus, the first total syntheses of NPD1 methyl ester epimer (which can also be considered as an enantiomer of AT‐NPD1) and its n‐3 docosapentaenoic acid derived analogue were achieved from a highly functionalized and late advanced pivotal intermediate. This innovative route may be easily adapted to gain access to other dihydroxylated metabolites and analogues of polyunsaturated fatty acids containing a conjugated E,E,Z‐triene subunit. Different epimers/diastereoisomers may be obtained by purchasing the suitable optically pure (S)‐ and/or (R)‐1,2,4‐butanetriol(s) as a chiral pool for both stereogenic centers.
Covalently Linked 5,15‐Diazaporphyrin Dimers: Promising Scaffolds for a Highly Conjugated Azaporphyrin π System
Authors: Matano Yoshihiro , Fujii Daisuke , Shibano Tarou , Furukawa Ko , Higashino Tomohiro , Nakano Haruyuki , Imahori Hiroshi 
Published: February 2014

AbstractThe first examples of β–β directly linked, acetylene‐bridged, and butadiyne‐bridged 5,15‐diazaporphyrin dimers have been prepared by palladium‐catalyzed coupling reactions of nickel(II) and copper(II) complexes of 3‐bromo‐10,20‐dimesityl‐5,15‐diazaporphyrin (mesityl=2,4,6‐trimethylphenyl). The effects of the linking modes and meso‐nitrogen atoms on the structural, optical, electrochemical, and magnetic properties of the distributed π systems were investigated by using X‐ray crystallography, UV/Vis absorption spectroscopy, DFT calculations, cyclic voltammetry, and ESR spectroscopy. Both the electronic and steric effects of the meso‐nitrogen atoms play an important role in the highly coplanar geometry of the directly linked dimers. The direct β–β linkage produces enhanced π conjugation and electron‐spin coupling between the two diazaporphyrin units.
Study on Distribution Features of Crustal Magnetic Anomalies Around Eastern Himalayan Syntaxis
Authors: Guo‐Fa KANG , Guo‐Ming GAO , Chun‐Hua BAI , Tian‐Yuan WANG , Yi‐Mi WANG , Teng ZHU 
Published: February 2014

AbstractThe Potsdam Magnetic Model of the Earth (POMME6.2) is used to investigate the spatial distribution of crustal magnetic anomalies around eastern Himalayan syntaxis and their decay with altitude. In order to study the different scales of magnetic anomalies, the two‐dimensional wavelet transform method is employed to decompose the ground magnetic anomalies. The relationship between magnetic anomaly and geological structure is also discussed. The results show that the distribution of crustal magnetic anomalies over study area is considerably non‐uniform. Relatively strong negative magnetic anomalies are distributed over Himalaya‐Eastern Syntaxis‐Longmen Mountains‐Daba Mountains, whereas positive magnetic anomalies are present over Sichuan Basin, with weaker magnetic anomalies over other regions. The eastern Himalaya syntaxis has important impact on magnetic anomalies around. All crustal magnetic anomalies over Eastern Syntaxis and the surrounding regions are medium‐ and short‐wavelength positive/negative ones superposed onto a negative or weak magnetic anomaly setting. These meso‐ and micro‐scale magnetic anomalies are generated from magnetic materials in the upper and middle crust, with strikes basically consistent with geological structures. Along Jinshajiang‐Honghe Fault Belt, there is a sharp weak magnetic anomaly belt. Longmenshan Fault Belt, Lijiang‐Xiaojinhe Fault Belt and Honghe Fault Belt are transitional zones between strong and weak magnetic anomalies. The east‐west magnetic anomalies in the central Tibetan Plateau exhibited arc shape in the dome of Eastern Syntaxis. The banded lumpy magnetic anomalies over the central Tibetan Plateau and Central Yunnan massif have the same decay rule.
Calculation of Coupling Coefficients for Component‐Type Borehole Strain Observations
Authors: Ling‐Kong ZHANG , An‐Fu NIU 
Published: February 2014

AbstractBased on the mechanical model for strain measurement in double bushing boreholes, we deduce formulae of two coupling coefficients (A, B) of each strain component under plane stress state. This provides a basis for further determining values and directions of maximum and minimum principal strains of the crustal strain field, and has some significance for carrying out borehole strain observations of earthquakes, volcanoes and plate boundaries. Using a two‐ring model and the complex variable function method, we calculate the c (area strain response coefficient) and d (shear strain response factor), and demonstrate that there exist relationships c = 2A and d = 2B. And the variation curves of both are identical. Their physical meanings are coupling coefficients in the borehole for measurement of plane strain and shear strain in crust.
Long‐Period Tides and Global Earthquake Energy Release
Authors: Chao‐Di XIE , Xiao‐Ping WU , Xing‐Lin LEI , Wei MAO , Nan SUN 
Published: February 2014

AbstractUsing USGS global catalog of M ≥ 5.0 earthquakes between 1850 and 2012, a time series of global seismic energy is set up. The wavelet transform is applied to these time series in order to analyze their quasi‐period characteristics. The results show that the time series of global seismic energy contains three quasi‐periodicity components of 9‐year, 19‐year and 45‐year, and the 45‐year quasi periodicity is most prominent. Combined with the physical background of the periodicities of tidal forces, the correlations between long‐period tidal forces and quasi periodicity of seismic energy release are discussed. Quasi‐period component related to short‐periodic tides is not found in global seismic energy release.
A fast implementation of the first fit contiguous partitioning strategy for cubic topologies
Authors: Pascual Jose A. , Miguel‐Alonso Jose , Lozano Jose A. 
Published: February 2014

SUMMARYIn this paper, we propose and evaluate improved first fit (IFF), a fast implementation of the first fit contiguous partitioning strategy. It has been devised to accelerate the process of finding contiguous partitions in space‐shared parallel computers in which the nodes are arranged forming multidimensional cubic networks. IFF uses system status information to drastically reduce the cost of finding partitions with the requested shape. The use of this information, i combined with the early detection of zones where requests cannot be allocated, remarkably improves the search speed in large networks. An exhaustive set of simulation‐based experiments have been carried out to test IFF against other algorithms implementing the same partitioning strategy. Results, using synthetic and real workloads, show that IFF can be several orders of magnitude faster than competitor algorithms. Copyright © 2013 John Wiley & Sons, Ltd.
IR Probes of Protein Microenvironments: Utility and Potential for Perturbation
Authors: Adhikary Ramkrishna , Zimmermann Jörg , Dawson Philip E. , Romesberg Floyd E. 
Published: February 2014

AbstractA variety of IR‐active moieties with absorptions that are distinct from those of proteins have been developed as probes of local protein environments, including carbon‐deuterium bonds (CD), cyano groups (CN), and azides (N3); however, no systematic analysis of their utility in a protein has been published. Previously, we characterized the N‐terminal Src homology 3 domain of the murine adapter protein Crk‐II (nSH3) with CD bonds site‐selectively incorporated throughout, and showed that it is relatively rigid and electrostatically heterogeneous and that it thermally unfolds under equilibrium conditions via a simple two‐state mechanism. We now report the synthesis and characterization of eight variants of nSH3 with CN and/or N3 probes at five of the same positions. In agreement with previous studies, the position‐dependent spectra suggest that both probes are predominantly sensitive to hydration, and not to their local electrostatic environments. Importantly, both probes also tend to significantly perturb the protein if they are not incorporated at surface‐exposed positions. Thus, unlike CD labels, which are both sensitive to their environment and non‐perturbative, CN and N3 probes should be used with caution.
Quantitative analysis of F‐actin redistribution in astrocytoma cells treated with candidate pharmaceuticals
Authors: Lockett Stephen , Verma Chrissie , Brafman Alla , Gudla Prabhakar , Nandy Kaustav , Mimaki Yoshihiro , Fuchs Philip L. , Jaja Joseph , Reilly Karlyne M. , Beutler John , Turbyville Thomas J. 
Published: February 2014

AbstractActin fibers (F‐actin) control the shape and internal organization of cells, and generate force. It has been long appreciated that these functions are tightly coupled, and in some cases drive cell behavior and cell fate. The distribution and dynamics of F‐actin is different in cancer versus normal cells and in response to small molecules, including actin‐targeting natural products and anticancer drugs. Therefore, quantifying actin structural changes from high resolution fluorescence micrographs is necessary for further understanding actin cytoskeleton dynamics and phenotypic consequences of drug interactions on cells. We applied an artificial neural network algorithm, which used image intensity and anisotropy measurements, to quantitatively classify F‐actin subcellular features into actin along the edges of cells, actin at the protrusions of cells, internal fibers and punctate signals. The algorithm measured significant increase in F‐actin at cell edges with concomitant decrease in internal punctate actin in astrocytoma cells lacking functional neurofibromin and p53 when treated with three structurally‐distinct anticancer small molecules: OSW1, Schweinfurthin A (SA) and a synthetic marine compound 23'‐dehydroxycephalostatin 1. Distinctly different changes were measured in cells treated with the actin inhibitor cytochalasin B. These measurements support published reports that SA acts on F‐actin in NF1−/− neurofibromin deficient cancer cells through changes in Rho signaling. Quantitative pattern analysis of cells has wide applications for understanding mechanisms of small molecules, because many anti‐cancer drugs directly or indirectly target cytoskeletal proteins. Furthermore, quantitative information about the actin cytoskeleton may make it possible to further understand cell fate decisions using mathematically testable models. Published 2014 Wiley Periodicals Inc.
Quantitative absorption cytometry for measuring red blood cell hemoglobin mass and volume
Authors: Schonbrun Ethan , Malka Roy , Di Caprio Giuseppe , Schaak Diane , Higgins John M. 
Published: February 2014

AbstractWe present an optical system, called the quantitative absorption cytometer (QAC), to measure the volume and hemoglobin mass of red blood cells flowing through a microfluidic channel. In contrast to clinical hematology analyzers, where cells are sphered in order for both volume and hemoglobin to be measured accurately, the QAC measures cells in their normal physiological shape. Human red blood cells are suspended in a refractive index‐matching absorbing buffer, driven through a microfluidic channel, and imaged using a transmission light microscope onto a color camera. A red and a blue LED illuminate cells and images at each color are used to independently retrieve cell volume and hemoglobin mass. This system shows good agreement with red blood cell indices retrieved by a clinical hematology analyzer and in fact measures a smaller coefficient of variation of hemoglobin concentration. In addition to cell indices, the QAC returns height and mass maps of each measured cell. These quantitative images are valuable for analyzing the detailed morphology of individual cells as well as statistical outliers found in the data. We also measured red blood cells in hypertonic and hypotonic buffers to quantify the correlation between volume and hemoglobin mass under osmotic stress. Because this method is invariant to cell shape, even extremely nonspherical cells in hypertonic buffers can be measured accurately. © 2014 International Society for Advancement of Cytometry