bluuebunny/crossref_metadata_2025_split huggingface dataset:
Eruptions at Lone Star geyser, Yellowstone National Park, USA: 2. Constraints on subsurface dynamics
Authors: Vandemeulebrouck Jean , Sohn Robert A. , Rudolph Maxwell L. , Hurwitz Shaul , Manga Michael , Johnston Malcolm J. S. , Soule S. Adam , McPhee Darcy , Glen Jonathan M. G. , Karlstrom Leif , Murphy Fred 
Published: October 2014

AbstractWe use seismic, tilt, lidar, thermal, and gravity data from 32 consecutive eruption cycles of Lone Star geyser in Yellowstone National Park to identify key subsurface processes throughout the geyser's eruption cycle. Previously, we described measurements and analyses associated with the geyser's erupting jet dynamics. Here we show that seismicity is dominated by hydrothermal tremor (~5–40 Hz) attributed to the nucleation and/or collapse of vapor bubbles. Water discharge during eruption preplay triggers high‐amplitude tremor pulses from a back azimuth aligned with the geyser cone, but during the rest of the eruption cycle it is shifted to the east‐northeast. Moreover, ~4 min period ground surface displacements recur every 26 ± 8 min and are uncorrelated with the eruption cycle. Based on these observations, we conclude that (1) the dynamical behavior of the geyser is controlled by the thermo‐mechanical coupling between the geyser conduit and a laterally offset reservoir periodically filled with a highly compressible two‐phase mixture, (2) liquid and steam slugs periodically ascend into the shallow crust near the geyser system inducing detectable deformation, (3) eruptions occur when the pressure decrease associated with overflow from geyser conduit during preplay triggers an unstable feedback between vapor generation (cavitation) and mass discharge, and (4) flow choking at a constriction in the conduit arrests the runaway process and increases the saturated vapor pressure in the reservoir by a factor of ~10 during eruptions.
Electromagnetic activity before initial breakdown pulses of lightning
Authors: Marshall T. , Stolzenburg M. , Karunarathna N. , Karunarathne S. 
Published: October 2014

AbstractLightning flash initiation is studied using electric field change (E‐change) measurements made in Florida. An initial E‐change (IEC) was found immediately before the first initial breakdown (IB) pulse in both cloud‐to‐ground (CG) and intracloud (IC) flashes if the E‐change sensor was within 80% of the reversal distance of the IEC. For 18 CG flashes, the IECs had an average point dipole moment of 23 C m and an average duration of 0.18 ms; these parameters for 18 IC flashes were −170 C m and 1.53 ms. The IECs of CG flashes began with a change in the slope of the E‐change (with respect to time) from zero slope to a positive slope, consistent with downward motion of negative charge and/or upward motion of positive charge. For IECs of IC flashes, the beginning slope change was from zero to negative slope, consistent with upward motion of negative charge and/or downward motion of positive charge. During an IEC, the E‐change monotonically increased for CG flashes and monotonically decreased for IC flashes. In 14 of 36 cases, the IEC beginning was coincident with a discrete, impulsive source of VHF radiation; another 13 cases had at least one VHF source during the IEC or the first IB pulse. Before the IECs, there were no preliminary variations detected in the 36 flashes. It is hypothesized that lightning initiation begins with an ionizing event that causes the IEC and that the IEC enhances the ambient electric field to produce the first IB pulse.
Enhanced π‐Backdonation from Gold(I): Isolation of Original Carbonyl and Carbene Complexes
Authors: Joost Maximilian , Estévez Laura , Mallet‐Ladeira Sonia , Miqueu Karinne , Amgoune Abderrahmane , Bourissou Didier 
Published: October 2014

AbstractThe specific electronic properties of bent o‐carborane diphosphine gold(I) fragments were exploited to obtain the first classical carbonyl complex of gold [(DPCb)AuCO]+ (ν(CO)=2143 cm−1) and the diphenylcarbene complex [(DPCb)Au(CPh2)]+, which is stabilized by the gold fragment rather than the carbene substituents. These two complexes were characterized by spectroscopic and crystallographic means. The [(DPCb)Au]+ fragment plays a major role in their stability, as substantiated by DFT calculations. The bending induced by the diphosphine ligand substantially enhances π‐backdonation and thereby allows the isolation of carbonyl and carbene complexes featuring significant π‐bond character.
Total Synthesis of Gracilioether F: Development and Application of Lewis Acid Promoted Ketene–Alkene [2+2] Cycloadditions and Late‐Stage CH Oxidation
Authors: Rasik Christopher M. , Brown M. Kevin 
Published: October 2014

AbstractThe first synthesis of gracilioether F, a polyketide natural product with an unusual tricyclic core and five contiguous stereocenters, is described. Key steps of the synthesis include a Lewis acid promoted ketene–alkene [2+2] cycloaddition and a late‐stage carboxylic acid directed C(sp3)H oxidation. The synthesis requires only eight steps from norbornadiene.
Trifluoromethoxylation of Arenes: Synthesis of ortho‐Trifluoromethoxylated Aniline Derivatives by OCF3 Migration
Authors: Hojczyk Katarzyna N. , Feng Pengju , Zhan Chengbo , Ngai Ming‐Yu 
Published: October 2014

AbstractAryl trifluoromethoxylation by a two‐step sequence of O‐trifluoromethylation of N‐aryl‐N‐hydroxylamine derivatives and intramolecular OCF3 migration is presented. This protocol allows easy access to a wide range of synthetically useful ortho‐OCF3 aniline derivatives. In addition, it utilizes bench‐stable reagents, is operationally simple, shows high functional‐group tolerance, and is amenable to gram‐scale as well as one‐pot synthesis. A reaction mechanism of a heterolytic cleavage of the NOCF3 bond followed by recombination of the resulting nitrenium ion and trifluoromethoxide is proposed for the OCF3‐migration reaction.
Molybdenum Phosphosulfide: An Active, Acid‐Stable, Earth‐Abundant Catalyst for the Hydrogen Evolution Reaction
Authors: Kibsgaard Jakob , Jaramillo Thomas F. 
Published: October 2014

AbstractIntroducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non‐noble‐metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed‐metal alloy catalysts are well‐known, MoP|S represents a more uncommon mixed‐anion catalyst where synergistic effects between sulfur and phosphorus produce a high‐surface‐area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water‐splitting cells.
Acetamide‐modified hyper‐cross‐linked resin: Synthesis, characterization, and adsorption performance to phenol from aqueous solution
Authors: Wang Xiaomei , Patil Prafulla D. , He Chunlian , Huang Jianhan , Liu You‐Nian 
Published: October 2014

ABSTRACTAcetamide‐modified hyper‐cross‐linked resin, HCP‐HMTA‐AA, was prepared and its adsorption performance was evaluated using phenol as the adsorbate. The prepared HCP–HMTA–AA owned predominant micro/mesopores and medium polarity, making it possess a superior adsorption to phenol as compared with polystyrene (PS), chloromethylated polystyrene (CMPS), hyper‐cross‐linked polymer (HCP) and amino‐modified hyper‐cross‐linked resin (HCP–HMTA). The adsorption enthalpy was −99.56 kJ/mol at zero fractional loading, multiple hydrogen bonding contributed to such a great adsorption enthalpy and an approximately planar hexahydric ring was formed between acetamide of HCP–HMTA–AA and phenol. The dynamic capacity of phenol on HCP–HMTA–AA was 291.3 mg/g at a feed concentration of 946.2 mg/L and a flow rate of 48 mL/h and the resin column was almost regenerated by a mixed solvent including 50% of ethanol (v/v) and 0.01 mol/L of sodium hydroxide (w/v). HCP–HMTA–AA was repeatedly used for five times and the equilibrium adsorption capacity for the five time reached 94.2% of the equilibrium adsorption capacity for the first time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41597.
Cellulose nanocrystal driven crystallization of poly(d,l‐lactide) and improvement of the thermomechanical properties
Authors: Camarero‐Espinosa Sandra , Boday Dylan J. , Weder Christoph , Foster E. Johan 
Published: October 2014

ABSTRACTThe technological exploitation of polylactide in fields requiring wide range of operating conditions is limited by the low crystallization rate of the polymer and therewith the low thermomechanical stability. Here we report the crystallization and consequent improvement of the thermomechanical properties of originally amorphous poly(d,l‐lactide) (d : l ratio 11 : 89) loaded with cellulose nanocrystals (CNCs). Isothermal treatment of samples with different CNC contents and at various temperatures, showed up to 6 wt % crystalline phase formation, as confirmed by differential scanning calorimetry and X‐ray diffraction measurements. Under a particular set of annealing conditions, CNCs promote the formation of a lamellar structure. This provides the system with higher order and cohesion which in combination with stress‐transfer between CNCs, led to an increase of the storage modulus in the rubbery plateau up to 30 times (from 2.7 MPa up to 79 MPa), a rise of the melting temperature up to 50°C, and an improvement of the Young's modulus up to 40%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41607.
Synthesis, characterization, and properties of acrylate‐modified tung‐oil waterborne insulation varnish
Authors: Ge Qing , Wang Hualin , She Yi , Jiang Suwei , Cao Mengye , Zhai Linfeng , Jiang Shaotong 
Published: October 2014

ABSTRACTAn acrylate‐modified tung‐oil waterborne insulation varnish was synthesized from tung oil, maleic anhydride, and acrylates via a Diels–Alder reaction and free‐radical polymerization, and the varnish could be solidified at a relatively low temperature with blocked hexamethylene diisocyanate as a curing agent. The resulting films were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The insulation properties (electrical insulation strength, volume resistivity, and surface resistivity) of the varnish films were tested, and the resistances of films to salted water were evaluated. With an increase in the maleic anhydride content, the thermal stability of the film was improved, whereas the electrical insulation strength, volume resistivity, and surface resistivity decreased. The electrical insulation strength of the film after it was immersed in the NaCl solution was lower than that in dry state, and it decreased as the immersed time was prolonged. In particular, the electrical insulation strength loss of the film increased significantly at maleic anhydride contents beyond 25 wt %. Furthermore, the hardness of the film increased with increasing methyl methacrylate/N‐butyl acrylate ratio, whereas the flexibility and adhesion of film decreased to a certain degree at the same time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41608.
Studies on thermal behavior, moisture absorption, and biodegradability of ginger spent incorporated polyurethane green composites
Authors: Chethana M. , Prashantha Kalappa , Siddaramaiah  
Published: October 2014

ABSTRACTEcological concern on accumulation of neutraceutical industrial waste material and the demands for newer composite materials have promoted extensive research on utilizing industrial wastes materials. Therefore, in the present study finely powdered ginger spent (GS), filled polyurethane (PU) green composites with varying amount viz., 0, 2.5, 5, 7.5, and 10 wt % of GS have been fabricated. The prepared PU/GS green composites have been characterized for their mechanical properties, density and void content. Interaction between filler and matrix has been confirmed from Fourier transform infrared spectroscopy studies. Moisture absorption and desorption studies have been performed at different relative humidity (RH). The moisture absorption and desorption studies, shows that as the hydrophilic GS content increases in the matrix the RH also increases. Water uptake behavior of PU/GS were measured in different chemical environments such as 5% sodium chloride solution, cold water at different temperature and in hydrochloric acid solution. The water uptake values increases as increase in GS concentration. Equilibrium water content, diffusivity and equilibrium time taken for all PU/GS composites have been investigated. Biodegradation studies reveals that as the GS content increases the weight loss also increases. Thermal properties have been performed using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). From DSC and DMA thermograms it is revealed that increase inTgwith increase in GS content. RH and contact angle measurement have been performed to understand the hydrophilic nature of the prepared composite. The morphological behavior of composites has been studied using scanning electron microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 41614.
A Necessary and Sufficient Condition for Stabilization of Switched Descriptor Time‐Delay Systems Under Arbitrary Switching
Authors: Zhao Jiemei , Zhang Lijun , Qi Xue 
Published: October 2014

AbstractIn this paper, a necessary and sufficient condition for generalized quadratic stabilization of switched descriptor time‐delay (SDT) systems under arbitrary switching is investigated. Based on the linear matrix inequality (LMI) method, some results are given: (i) the SDT system is regular, impulse‐free, and stable under arbitrary switching; (ii) the necessary and sufficient condition for switched generalized quadratic stability (stabilization) of the uncertain SDT systems is derived. Finally, a numerical example is provided to illustrate the effectiveness of the method.
Selective extraction based on poly(MAA‐VB‐EGMDA) monolith followed by HPLC for determination of hordenine in plasma and urine samples
Authors: Chen Yonggang , Meng Junhua , Zou Jili , An Jing 
Published: October 2014

AbstractHordenine is an active compound found in several foods, herbs and beer. In this work, a novel sorbent was fabricated for selective solid‐phase extraction (SPE) of hordenine in biological samples. The organic polymer sorbent was synthesized in one step in the plastic barrel of a syringe by a pre‐polymerization solution consisting of methacrylic acid (MAA), 4‐vinylphenylboronic acid (VB) and ethylene glycol dimethacrylate (EGDMA). The conditions for preparation were optimized to generate a poly(MAA‐VB‐EGMDA) monolith with good permeability. The monolith exhibited good enrichment efficiency towards hordenine. By using tyramine as the internal standard, a poly(MAA‐VB‐EGMDA)‐based SPE‐HPLC method was established for analysis of hordenine. Conditions for SPE, including volume of eluting solvent, pH of sample solution, sampling rate and sample volume, were optimized. The proposed SPE‐HPLC method presented good linearity (R2 = 0.9992) within 10–2000 ng/mL and the detection limits was 3 ng/mL, which is significantly more sensitive than reported methods. The method was also applied in plasma and urine samples; good capability of removing matrices was observed, while hordenine in low content was well extracted and enriched. The recoveries were from 90.6 to 94.7% and from 89.3 to 91.5% for the spiked plasma and urine samples, respectively, with the relative standard deviations <4.7%. Copyright © 2014 John Wiley & Sons, Ltd.
Qualitative and quantitative analysis of the major constituents in Acorus tatarinowii Schott by HPLC/ESI‐QTOF‐MS/MS
Authors: Zhang Feng , Qi Peng , Xue Rui , Li Zhixiong , Zhu Kaicheng , Wan Ping , Huang Chenggang 
Published: October 2014

AbstractAcorus tatarinowii Schott (ATS) is a well‐known traditional Chinese medicine (TCM) for the treatment of epilepsy, amnesia and insomnia. In this study, a methodology utilizing high‐performance liquid chromatography (HPLC) coupled with electrospray ionization quadrupole time‐of‐flight mass spectrometry (ESI‐QTOF‐MS/MS) was established for the separation and structural identification of the major chemical constituents in ATS for the first time. Overall, 46 major constituents including flavonoid glycosides, phenylpropane derivatives, amides and lignans were identified or tentatively characterized. Seven major constituents, including four phenylpropane derivatives and three lignans, were further quantified as marker substances, which showed good linearity within the test ranges. These results indicated that the developed quantitative method was linear, sensitive, and precise for quality control of ATS. Copyright © 2014 John Wiley & Sons, Ltd.
Vismodegib, an antagonist of hedgehog signaling, directly alters taste molecular signaling in taste buds
Authors: Yang Hyekyung , Cong Wei‐na , Yoon Jeong Seon , Egan Josephine M. 
Published: October 2014

AbstractVismodegib, a highly selective inhibitor of hedgehog (Hh) pathway, is an approved treatment for basal‐cell carcinoma. Patients on treatment with vismodegib often report profound alterations in taste sensation. The cellular mechanisms underlying the alterations have not been studied. Sonic Hh (Shh) signaling is required for cell growth and differentiation. In taste buds, Shh is exclusively expressed in type IV taste cells, which are undifferentiated basal cells and the precursors of the three types of taste sensing cells. Thus, we investigated if vismodegib has an inhibitory effect on taste cell turnover because of its known effects on Hh signaling. We gavaged C57BL/6J male mice daily with either vehicle or 30 mg/kg vismodegib for 15 weeks. The gustatory behavior and immunohistochemical profile of taste cells were examined. Vismodegib‐treated mice showed decreased growth rate and behavioral responsivity to sweet and bitter stimuli, compared to vehicle‐treated mice. We found that vismodegib‐treated mice had significant reductions in taste bud size and numbers of taste cells per taste bud. Additionally, vismodegib treatment resulted in decreased numbers of Ki67‐ and Shh‐expressing cells in taste buds. The numbers of phospholipase Cβ2‐ and α‐gustducin‐expressing cells, which contain biochemical machinery for sweet and bitter sensing, were reduced in vismodegib‐treated mice. Furthermore, vismodegib treatment resulted in reduction in numbers of T1R3, glucagon‐like peptide‐1, and glucagon‐expressing cells, which are known to modulate sweet taste sensitivity. These results suggest that inhibition of Shh signaling by vismodegib treatment directly results in alteration of taste due to local effects in taste buds.
Cytochrome P450 OxyBtei Catalyzes the First Phenolic Coupling Step in Teicoplanin Biosynthesis
Authors: Haslinger Kristina , Maximowitsch Egle , Brieke Clara , Koch Alexa , Cryle Max J. 
Published: October 2014

AbstractBacterial cytochrome P450s form a remarkable clade of the P450 superfamily of oxidative hemoproteins, and are often involved in the biosynthesis of complex natural products. Those in a subgroup known as “Oxy enzymes” play a crucial role in the biosynthesis of glycopeptide antibiotics, including vancomycin and teicoplanin. The Oxy enzymes catalyze crosslinking of aromatic residues in the non‐ribosomal antibiotic precursor peptide while it remains bound to the non‐ribosomal peptide synthetase (NRPS); this crosslinking secures the three‐dimensional structure of the glycopeptide, crucial for antibiotic activity. We have characterized OxyBtei, the first of the Oxy enzymes in teicoplanin biosynthesis. Our results reveal that OxyBtei possesses a structure similar to those of other Oxy proteins and is active in crosslinking NRPS‐bound peptide substrates. However, OxyBtei displays a significantly altered activity spectrum against peptide substrates compared to its well‐studied vancomycin homologue.
Ni–Co/Al2O3Bimetallic Catalysts for CH4Steam Reforming: Elucidating the Role of Co for Improving Coke Resistance
Authors: You Xiaojuan , Wang Xiang , Ma Youhe , Liu Jianjun , Liu Wenming , Xu Xianglan , Peng Honggen , Li Changqing , Zhou Wufeng , Yuan Ping , Chen Xiaohong 
Published: October 2014

AbstractA series of supported Ni–Co/γ‐Al2O3bimetallic catalysts with a fixed 12 % Ni loading but different Co contents were prepared by using the coimpregnation method and investigated for methane steam reforming. The addition of Co can significantly improve the coke resistance and the reaction stability of Ni/Al2O3at a mild loss of the reforming activity. XPS and TEM results prove the existence of strong interaction between Ni and Co species. XRD and high‐angle annular dark‐field scanning transmission electron microscopy mapping results of the reduced catalysts provide direct evidence for surface Ni–Co alloy formation upon Co addition onto Ni/Al2O3, which can block part of the active low coordinated Ni sites and lower the metal dispersion, thus effectively suppressing coking and improving the reaction stability in comparison with the unmodified Ni/Al2O3catalyst.
Highly Phosphorescent Supramolecular Hydrogels Based on Platinum Emitters
Authors: Allampally Naveen Kumar , Bredol Michael , Strassert Cristian A. , De Cola Luisa 
Published: October 2014

AbstractWe have synthesised a neutral, water‐soluble, PtII complex able to aggregate more efficiently in aqueous solutions than in organic solvents. The aggregates are luminescent and are not quenched by molecular oxygen. Further, we have prepared phosphorescent hydrogels utilising host–guest interactions between cyclodextrins and the tetraethylene glycol tails of the PtII complex. The soft assemblies feature host‐dependent emission properties.