bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ruthenium‐Catalyzed Hydrogenation of Oxygen‐Functionalized Aromatic Compounds in Water
Authors: Jantke Dominik , Cokoja Mirza , Drees Markus , Herrmann Wolfgang A. , Kühn Fritz E. 
Published: August 2013

AbstractThe application of a ruthenium complex, bearing a sulfonated bis‐N‐heterocyclic carbene (NHC) ligand as catalyst precursor for the hydrogenation of aromatic compounds is reported. The reaction proceeds under mild conditions in aqueous phase. The treatment of the Ru complex with 40 bar H2 at 60 °C in water (0.1 M KOH solution) leads to the formation of a catalytically active species, which can be stored and used in catalysis experiments. The catalyst is responsible for the hydrogenation of functionalized aromatic substrates exhibiting endo‐ and exo‐CO bonds, which are relevant products in biomass conversion. Acetophenone is quantitatively reduced to 1‐cyclohexyl ethanol with a selectivity of 100 %. Various other oxygen‐functionalized aromatic substrates were also hydrogenated in moderate to quantitative conversions. To elucidate the nature of the catalytically active species, NMR, UV/vis, and ESI‐MS experiments were undertaken, showing the presence of a mononuclear Ru hydride complex. TEM measurements of a sample of the catalyst solution did not indicate the presence of nanoparticles. Mechanistic investigations point towards a homogenous mechanism.
Identification of Molecular Crystals Capable of Undergoing an Acyl‐Transfer Reaction Based on Intermolecular Interactions in the Crystal Lattice
Authors: Tamboli Majid I. , Krishnaswamy Shobhana , Gonnade Rajesh G. , Shashidhar Mysore S. 
Published: August 2013

AbstractInvestigation of the intermolecular acyl‐transfer reactivity in molecular crystals of myo‐inositol orthoester derivatives and its correlation with crystal structures enabled us to identify the essential parameters to support efficient acyl‐transfer reactions in crystals: 1) the favorable geometry of the nucleophile (OH) and the electrophile (CO) and 2) the molecular assembly, reinforced by CH⋅⋅⋅π interactions, which supports a domino‐type reaction in crystals. These parameters were used to identify another reactive crystal through a data‐mining study of the Cambridge Structural Database. A 2:1 co‐crystal of 2,3‐naphthalene diol and its di‐p‐methylbenzoate was selected as a potentially reactive crystal and its reactivity was tested by heating the co‐crystals in the presence of solid sodium carbonate. A facile intermolecular p‐toluoyl group transfer was observed as predicted. The successful identification of reactive crystals opens up a new method for the detection of molecular crystals capable of exhibiting acyl‐transfer reactivity.
Butterfly‐Shaped Pentanuclear Dysprosium Single‐Molecule Magnets
Authors: Tian Haiquan , Zhao Lang , Lin Haifeng , Tang Jinkui , Li Guangshe 
Published: August 2013

AbstractTwo new “butterfly‐shaped” pentanuclear dysprosium(III) clusters, [Dy5(μ3‐OH)3(opch)6(H2O)3]⋅3 MeOH⋅ 9 H2O (1) and [Dy5(μ3‐OH)3(Hopch)2(opch)4(MeOH)(H2O)2]⋅(ClO4)2⋅ 6 MeOH⋅4 H2O (2), which were based on the heterodonor‐chelating ligand o‐vanillin pyrazine acylhydrazone (H2opch), have been successfully synthesized by applying different reaction conditions. Single‐crystal X‐ray diffraction analysis revealed that the butterfly‐shaped cores in both compounds were comparable. However, their magnetic properties were drastically different. Indeed, compound 1 showed dual slow‐relaxation processes with a transition between them that corresponded to energy gaps (Δ) of 8.1 and 37.9 K and pre‐exponential factors (τ0) of 1.7×10−5 and 9.7×10−8 s for the low‐ and high‐temperature domains, respectively, whilst only a single relaxation process was noted for compound 2 (Δ=197 K, τ0=3.2×10−9 s). These significant disparities are most likely due to the versatile coordination of the H2opch ligands with particular keto–enol tautomerism, which alters the strength of the local crystal field and, hence, the nature or direction of the easy axes of anisotropic dysprosium ions.
Alkaline Earth Metallocenes Coordinated with Ester Pendants: Synthesis, Structural Characterization, and Application in Metathesis Reactions
Authors: Li Heng , Zhang Wen‐Xiong , Xi Zhenfeng 
Published: August 2013

AbstractA variety of ester‐substituted cyclopentadiene derivatives have been synthesized by one‐pot reactions of 1,4‐dilithio‐1,3‐butadienes, CO, and acid chlorides. Direct deprotonation of the ester‐substituted cyclopentadienes with Ae[N(SiMe3)2]2 (Ae=Ca, Sr, Ba) efficiently generated members of a new class of heavier alkaline earth (Ca, Sr, Ba) metallocenes in good to excellent yields. Single‐crystal X‐ray structural analysis demonstrated that these heavier alkaline earth metallocenes incorporated two intramolecularly coordinated ester pendants and multiply‐substituted cyclopentadienyl ligands. The corresponding transition metal metallocenes, such as ferrocene derivatives and half‐sandwich cyclopentadienyl tricarbonylrhenium complexes, could be generated highly efficiently by metathesis reactions. The multiply‐substituted cyclopentadiene ligands bearing an ester pendant, and the corresponding heavier alkaline earth and transition‐metal metallocenes, may have further applications in coordination chemistry, organometallic chemistry, and organic synthesis.
Nucleoside Analogues with a 1,3‐DieneFe(CO)3 Substructure: Stereoselective Synthesis, Configurational Assignment, and Apoptosis‐Inducing Activity
Authors: Hirschhäuser Christoph , Velcicky Juraj , Schlawe Daniel , Hessler Erik , Majdalani André , Neudörfl Jörg‐Martin , Prokop Aram , Wieder Thomas , Schmalz Hans‐Günther 
Published: August 2013

AbstractThe synthesis and stereochemical assignment of two classes of iron‐containing nucleoside analogues, both of which contain a butadieneFe(CO)3 substructure, is described. The first type of compounds are Fe(CO)3‐complexed 3′‐alkenyl‐2′,3′‐dideoxy‐2′,3′‐dehydro nucleosides (2,5‐dihydrofuran derivatives), from which the second class of compounds is derived by formal replacement of the ring oxygen atom by a CH2 group (carbocyclic nucleoside analogues). These compounds were prepared in a stereoselective manner through the metal‐assisted introduction of the nucleobase. Whilst the furanoid intermediates were prepared from carbohydrates (such as methyl‐glucopyranoside), the carbocyclic compounds were obtained by using an intramolecular Pauson–Khand reaction. Stereochemical assignments based on NMR and CD spectroscopy were confirmed by X‐ray structural analysis. Biological investigations revealed that several of the complexes exhibited pronounced apoptosis‐inducing properties (through an unusual caspase 3‐independent but ROS‐dependent pathway). Furthermore, some structure–activity relationships were identified, also as a precondition for the design and synthesis of fluorescent and biotin‐labeled conjugates.
Growth of Au@Ag Core–Shell Pentatwinned Nanorods: Tuning the End Facets
Authors: Zhang Weiqing , Goh Hao Ying Johnny , Firdoz Shaik , Lu Xianmao 
Published: August 2013

AbstractAu@Ag core–shell nanorods with tunable end facets are obtained by coating Au bipyramids (BPs) with Ag. The resultant nanorods exhibit a pentatwinned crystal structure with tips terminated with either {110} or {111} facets. The control over the end facets is achieved by varying the capping agents and tuning the reduction rate of Ag. Specifically, when Ag is reduced slowly, Au@Ag nanorods with flat {110} end facets are formed with cetyltrimethylammonium bromide (CTAB) as the capping agent. If CTAB is replaced with cetyltrimethylammonium chloride (CTAC), Au@Ag nanorods with tips terminated with {111} facets are obtained. However, at a high Ag reduction rate, dumbbell‐shaped Au@Ag nanorods are formed, with either CTAB or CTAC as the capping agent. The morphological evolution of the nanorods in each case is closely followed and a growth mechanism is proposed.
Adsorption and catalytic ozonation performance of activated carbon and cobalt‐supported activated carbon derived from brewing yeast
Authors: Wu Guiping , Wei Wei , Cui Longzhe 
Published: August 2013

AbstractActivated carbon (AC) was prepared from brewing yeast by NaCO activation, and cobalt was supported on activated carbon (Co/AC) by the adsorption–activation method. The XPS test indicated that supported cobalt was Co(II). The total BET surface areas of prepared AC and Co/AC were 957.7 and 847.9 m/g, with total pore volumes of 0.81 and 0.80 cm/g, respectively. The average pore diameters of AC and Co/AC were found to be 3.8 and 3.3 nm. The contact time required for equilibrium of methylene blue (MB) adsorption onto prepared AC and Co/AC was about 120 min. The maximum uptake of MB by AC and Co/AC was estimated to be 372.1 and 213.5 mg/g, respectively. The presence of prepared AC or Co/AC was advantageous for TOC reduction compared with UV/O system, and the greatest TOC removal was obtained in the presence of Co/AC. The kinetics of the degradation of MB fitted the Langmuir‐first‐order model well. The rate constants of Langmuir first‐order were determined to be 0.0096 min−1 for UV/O/AC and 0.0143 min−1 for UV/O/Co/AC, respectively.
Background Features of Schumann Resonances Observed in Yunnan, Southwestern China
Authors: Xin‐Yan OUYANG , Xue‐Min ZHANG , Xu‐Hui SHEN , Wen‐Yu LOU , Yuan‐Qing MIAO 
Published: August 2013

AbstractThis paper presents the background features of Schumann resonances (SR) observed at the Yongsheng observatory in Yunnan, southwestern China. We calculated the hourly average of the frequency and power spectral density (PSD) of the lowest three SR modes, and analyzed diurnal variation of SR frequency and PSD both in BNS and BEW components around equinoxes and solstices. Diurnal variation of SR PSD is found to be related to the dominant intervals of Asian, African and American thunderstorm centers and the relative position of the observatory to three thunderstorm centers. Diurnal variation of SR frequency is more complicated. SR frequency and PSD at the lowest three modes around the summer solstice and autumn equinox are more variable than that in the spring equinox and winter solstice. The daily median of SR peak frequency in 2011 shows that seasonal variation of peak frequency is blurry, while annual variation of daily median of PSD shows a clear seasonal variation which resembled half a period of a sine curve and symmetrically distributed about July. The seasonal variation of PSD is in accordance with that of lightning activities. Frequency of the first mode is about at 7.5 Hz both in BNS and BEW components. However, with the higher mode, SR frequency in BNS component is 0.5 Hz larger than that in BEW component. The cause of this frequency shift is not clear yet.
The Exhumation Process of Mufushan Granite in Jiangnan Uplift Since Cenozoic: Evidence from Low‐Temperature Thermochronology
Authors: Hong‐Cai SHI , Xiao‐Bin SHI , Xiao‐Qiu YANG , Hai‐Yan JIANG 
Published: August 2013

AbstractJiangnan uplift located in the collision zone between Yangtze and Cathaysia block is the key to interpret the tectonic evolution of South China block. The Cenozoic thermal history and the uplift processes of Mufushan pluton are constrained by the combination of analysis of apatite fission track and (U‐Th‐Sm)/He ages with modeling of fission track length distribution. Based on the analysis of thermochronological dating and regional tectonic setting, the authors probed into the relationship between the thermochronological evolution and the tectonic development. The exhumation of plutons arrived at about 4800 m since 80 Ma, and the uplift processes were not uniform in space, and different plutons had somewhat different uplift processes. Thermal history modeling of the AFT data shows that the Mufushan pluton experienced three episodes of cooling event, two rapid exhumation events happened in Upper Cretaceous‐Paleocene (about 80∼50 Ma) and Upper Miocene (since 10 Ma). There is a period of relative thermal stability between 50 and 10 Ma. The first stage of rapid uplifting during 80∼50 Ma in this region is coeval with extension episode of Mid‐Upper Yangtze during Himalayan which resulted in the formation of fault basin and exhumation of shoulder block; the Upper Miocene rapid cooling since 10 Ma is attributed to the westward movement and subduction of Pacific plate. The uplift and exhumation of Mufushan pluton since Late Yanshanian led to a good deposition response in basins and the cooling events of three phases just coincided with the regional tectonic settings of study area.
A Study on Parallel Computation for 3D Magneto‐Telluric Modeling Using the Staggered‐Grid Finite Difference Method
Authors: Yan LI , Xiang‐Yun HU , Wen‐Cai YANG , Wen‐Bo WEI , Hui FANG , Bo HAN , Rong‐Hua PENG 
Published: August 2013

AbstractComputation time and memory requirements are two common problems for magnetotelluric (MT) modeling of three‐dimensional conductivity structure. We develop a new parallel processing scheme that can efficiently improve the computational speed of 3D MT modeling. The scheme of 3D MT modeling based on the staggered‐grid finite difference method is implemented in the frequency domain, and the calculation process of the EM field for each frequency is independent. Therefore, considering the naturally parallelizable character, the whole computation task of all frequencies can be divided into many minor calculation tasks for single or multiple frequencies, which will be assigned to different computing nodes and calculated in a parallel manner. In this work, by adopting master‐slave parallel mode and parallel computation with frequencies scheme, we have implemented the parallel computation of 3D MT modeling using MPI on the Dawn TC5000A high‐performance parallel platform. Furthermore, we tested our parallel algorithm of 3D MT modeling using two 3D theoretical models and analyzed the calculation efficiency on a multiple‐nodes computer, and the results show that the parallel algorithm is effective and efficient, which lays a solid foundation for subsequent three‐dimensional parallel MT inversion.
Correlation Between Space and Ground‐Based Observational Data in Their Near Direct Current Electric Field Background Characteristics
Authors: Rui YAN , Lan‐Wei WANG , Shi‐Zhong ZHANG , Zhe HU , Xing‐Guo ZHANG , Da‐Peng LIU , Xu ZHU , Yu ZHANG 
Published: August 2013

AbstractStudy of the characteristics of space‐ and ground‐based electromagnetic observational data, as well as the correlation between them, has important scientific significance for the combined application of both data to earthquake monitoring and research. In this paper, the near DC electromagnetic data recorded by the DEMETER satellite, vertical and horizontal geoelectric field data recorded at the Hongshawan station, and horizontal geoelectric field data recorded at the Chengdu station were comprehensively studied. The results show that observational data of the ULF electric field recorded directly by the DEMETER satellite do not indicate any significant annual change trends; the observational data from along the velocity vector direction on both the day and night sides present longer‐term cyclical characteristics, but no correlation or synchronization with the geoelectric field observational data. The magnitude of the electric field data in the ionosphere after removing the additional electric field values caused by the satellite cutting the magnetic line are consistent with the geoelectric field data, and concentrated at about 10−1∼ 10−2 mV/m. The concave annual seasonal change trends are displayed from the observation data along the normal to the orbit direction, and along the velocity vector direction on the night side, showing a relatively stable annual variation period, which is consistent with the trend of the annual variation of the horizontal geoelectric field. Therefore, it may be concluded that both the magnitude and annual trends have exhibited correlation and synchronization every year.
Seismic Imaging of Complex and Steep Structures in the Kuqa Depression
Authors: Li‐Yun FU , You‐Jun XIAO , Wei‐Jia SUN , Chao WU , Xi‐Zhu GUAN , Jing‐Zhou ZHANG 
Published: August 2013

AbstractSeismic imaging generally relies on data quality, velocity reliability, and migration operator performance. Complex near‐surface geological conditions in Kuqa depression cause extremely low signal‐to‐noise (S/N) ratios of seismic data. Salts penetrating into overthrust structures are widely distributed, vary in thickness and shape of complex geometries, and distort the imaging of subsalt faults, leading to complicated imaging problems. This article studies three key issues. In the preprocessing of prestack data, some innovative techniques combined with commercial techniques are employed by three levels to improve data quality and reconstruct the reflections from depths. Three‐stage migration velocity analyses, subtle DMO velocity analysis, prestack time‐migration, and prestack depth‐migration velocity analyses are implemented to build a topology‐preservation prestack‐migration velocity model. The time‐depth conversion of the prestack time‐migration velocity model is performed based on the Kuqa‐depression modeling of salt‐related overthrust complex structures combined with the velocity‐varying mapping technique. The well‐constrained seismic inversion for low‐frequency velocities is conducted to handle the syncretization of the well‐building and migration‐building velocity fields. Finally, prestack time and depth migrations are performed by a semi‐analytic degenerate Fourier migrator that improves the imaging of high‐wavenumber components. Applications to the Dabei, Bozi, Quele, Xiqiu10, and Xiqiu4 structures result in well‐positioned images for salt‐related overthrust complex structures.
Is FapyG Mutagenic?: Evidence from the DFT Study
Authors: Jena Nihar Ranjan , Mishra Phool Chand 
Published: August 2013

Abstract2,6‐diamino‐4‐oxo‐5‐formamidopyrimidine (FapyG) is an oxidatively damaged product of guanine (G), which is mainly formed through metabolic processes that produce OH radicals. It has been proposed that in bacterial cells, FapyG retains the coding properties of G, and is, therefore, not mutagenic. However, in mammalian cells, FapyG induces G to thymine (T) mutation more dominantly than another ubiquitous oxidative lesion, that is, 8‐oxoguanine (8‐oxoG). The exact reasons for these coding properties of FapyG are not properly understood. In order to rationalize the cause of FapyG‐mediated mutagenesis, all of the possible base‐pair interactions of FapyG with cytosine (C), adenine (A), and T, in both anti‐ and syn‐ conformations, are studied in detail by using density functional theory (DFT). The effects of solvation on the coding properties of FapyG are also evaluated. We demonstrate that the anti‐FapyG:C base pair has the highest binding energy, and that the base‐pair alignment is similar to that of the normal G:C base pair. Therefore, insertion of C opposite anti‐FapyG is preferred over the other DNA bases. This could be the reason for the non‐mutagenic behavior of FapyG in bacterial cells. However, as the binding patterns and energies of anti‐FpyG:A and syn‐FapyG:A base pairs are similar, and these are also similar to those of the T:A base pair, mammalian polymerases may not distinguish between FapyG and T. As a result, A would be mistakenly inserted opposite either anti‐FapyG or syn‐FapyG, resulting in G to T transverse mutation.
The immunopathogenesis of the HIV tuberculosis immune reconstitution inflammatory syndrome
Authors: Lai Rachel P. J. , Nakiwala Justine K. , Meintjes Graeme , Wilkinson Robert J. 
Published: August 2013

HIV‐1 patients co‐infected with some pathogens are at risk of developing the immune reconstitution inflammatory syndrome (IRIS) when initiating antiretroviral therapy (ART). IRIS is characterized by inflammation leading to the clinical worsening of a treated infection or the unmasking of a previously undiagnosed condition or infection. It is commonly associated with tuberculosis (TB), 8–43% of the HIV‐TB co‐infected patients prescribed with antitubercular treatment and ART develop TB‐IRIS. Although IRIS has been recognized for over 20 years, relatively little was known until recently about its pathogenesis. Despite these advances in understanding IRIS, there remains no immune biomarker for diagnostic or prognostic purposes. Here, we review the risk factors associated with TB‐IRIS, the challenges in studying this syndrome, and how T lymphocytes, dysregulated cytokine responses, and innate immunity may contribute to the development of TB‐IRIS.
Ferritic Cathodes Degradation by Potassium/Chromium Poisoning and Air Humidification
Authors: Arregui A. , Rodriguez‐Martinez L. M. , Modena S. , Bertoldi M. , Sglavo V. M. 
Published: August 2013

AbstractDegradation mechanisms inherent to ferritic LSF‐SDC and LSCF‐GDC cathodes are studied by post‐mortem analysis of cells which suffered the most significant performance deterioration in a set of 18 500 h tests carried out under a specific experimental design. Three cathode processing parameters (composition, thickness, and sintering temperature) were combined with five operation conditions (chromium presence, current density, operating temperature, air flow, and humidification) through this design of experiments based in a L18 Taguchi matrix. In the case of cells exposed to chromium vapors from Crofer 22 APU pieces, those cells which exhibited K2Cr2O7 deposition in the cathode/GDC barrier interface underwent the most aggressive ASR degradation. Similar deposits were also observed on the surface of LSC current collectors. Two cells exposed to highly humidified air (20%) exhibited cathode delamination and GDC barrier deterioration by crack propagation though no foreign elements diffusion to the interface could be detected.
Modifying a Stainless Steel for PEMFC Bipolar Plates via Electrochemical Nitridation
Authors: Wang H. , Turner J. A. 
Published: August 2013

AbstractAISI446 stainless steel was electrochemically nitrided at room temperature. X‐ray photoelectron spectroscopy (XPS) analysis indicated that the nitrided steel was covered with surface ammonia and a layer of nitrides (mainly of mixed chromium nitrides). The nitride layer for 4 h nitrided steel at –0.9 V was about 2.5 nm thick. Dominating oxides appear on the steel's surface, so nitrogen incorporated oxides is a suitable term to describe the nitrided surface. The nitrided surface showed very low interfacial contact resistance (ICR) and excellent corrosion resistance in simulated polymer electrolyte membrane fuel cell (PEMFC) environments. The excellent stability of the nitride steel was confirmed by XPS depth profiling before and after testing in the PEMFC environments. Electrochemical nitridation provides an economic way for modifying the steel's surface to approach the U.S. Department of Energy 2015 goal for bipolar plates.