bluuebunny/crossref_metadata_2025_split huggingface dataset:
Day‐to‐day variability of equatorial electrojet and its role on the day‐to‐day characteristics of the equatorial ionization anomaly over the Indian and Brazilian sectors
Authors: Venkatesh K. , Fagundes P. R. , Prasad D. S. V. V .D. , Denardini C. M. , de Abreu A. J. , de Jesus R. , Gende M. 
Published: September 2015

AbstractThe equatorial electrojet (EEJ) is a narrow band of current flowing eastward at the ionospheric E region altitudes along the dayside dip equator. Mutually perpendicular electric and magnetic fields over the equator results in the formation of equatorial ionization anomaly (EIA), which in turn generates large electron density variabilities. Simultaneous study on the characteristics of EEJ and EIA is necessary to understand the role of EEJ on the EIA variabilities. This is helpful for the improved estimation of total electron content (TEC) and range delays required for satellite‐based communication and navigation applications. Present study reports simultaneous variations of EEJ and GPS‐TEC over Indian and Brazilian sectors to understand the role of EEJ on the day‐to‐day characteristics of the EIA. Magnetometer measurements during the low solar activity year 2004 are used to derive the EEJ values over the two different sectors. The characteristics of EIA are studied using two different chains of GPS receivers along the common meridian of 77°E (India) and 45°W (Brazil). The diurnal, seasonal, and day‐to‐day variations of EEJ and TEC are described simultaneously. Variations of EIA during different seasons are presented along with the variations of the EEJ in the two hemispheres. The role of EEJ variations on the characteristic features of the EIA such as the strength and temporal extent of the EIA crest has also been reported. Further, the time delay between the occurrences of the day maximum EEJ and the well‐developed EIA is studied and corresponding results are presented in this paper.
Thermal conductivity of H2O‐CH3OH mixtures at high pressures: Implications for the dynamics of icy super‐Earths outer shells
Authors: Hsieh Wen‐Pin , Deschamps Frédéric 
Published: September 2015

AbstractThermal conductivity of H2O‐volatile mixtures at extreme pressure‐temperature conditions is a key factor to determine the heat flux and profile of the interior temperature in icy bodies. We use time domain thermoreflectance and stimulated Brillouin scattering combined with diamond anvil cells to study the thermal conductivity and sound velocity of water (H2O)‐methanol (CH3OH) mixtures to pressures as high as 12 GPa. Compared to pure H2O, the presence of 5–20 wt % CH3OH significantly reduces the thermal conductivity and sound velocity when the mixture becomes ice VI‐CH3OH and ice VII‐CH3OH phases at high pressures, indicating that the heat transfer is hindered within the icy body. We then apply these results to model the heat transfer through the icy mantles of super‐Earths, assuming that these mantles are animated by thermal convection. Our calculations indicate that the decrease of thermal conductivity due to the presence of 10 wt % CH3OH induces a twofold decrease of the power transported by convection.
Propane σ‐Complexes on PdO(101): Spectroscopic Evidence of the Selective Coordination and Activation of Primary CH Bonds
Authors: Zhang Feng , Pan Li , Choi Juhee , Mehar Vikram , Diulus John T. , Asthagiri Aravind , Weaver Jason F. 
Published: September 2015

AbstractAchieving selective CH bond cleavage is critical for developing catalytic processes that transform small alkanes to value‐added products. The present study clarifies the molecular‐level origin for an exceptionally strong preference for propane to dissociate on the crystalline PdO(101) surface via primary CH bond cleavage. Using reflection absorption infrared spectroscopy (RAIRS) and density functional theory (DFT) calculations, we show that adsorbed propane σ‐complexes preferentially adopt geometries on PdO(101) in which only primary CH bonds datively interact with the surface Pd atoms at low propane coverages and are thus activated under typical catalytic reaction conditions. We show that a propane molecule achieves maximum stability on PdO(101) by adopting a bidentate geometry in which a HPd dative bond forms at each CH3 group. These results demonstrate that structural registry between the molecule and surface can strongly influence the selectivity of a metal oxide surface in activating alkane CH bonds.
Ein robuster mesoionischer Pyridylcarben‐Cobalt‐Komplex als Elektrokatalysator für die Wasserstoff‐Produktion
Authors: van der Meer Margarethe , Glais Estelle , Siewert Inke , Sarkar Biprajit 
Published: September 2015

AbstractDas erste Beispiel für einen CoIII‐Komplex mit einem mesoionischen Pyridylcarben‐Liganden wird vorgestellt. Der Komplex ist ein effizienter Elektrokatalysator für die H2‐Produktion bei sehr niedriger Überspannung und sehr hohen Wechselzahlen unter Verwendung einer Glaskohlenstoff‐Arbeitselektrode. Die entsprechenden Triazol‐Komplexe zeigen keinerlei katalytische Aktivität unter identischen Bedingungen. Die bemerkenswerte Stabilität der Co‐C(Carben)‐Bindung gegenüber Säuren ist sehr wahrscheinlich ein Grund für die hohe Effizienz des Katalysators. Die vorliegenden Ergebnisse öffnen ein neues Forschungsgebiet für funktionale Hydrogenasemodelle unter Verwendung von Carben‐basierten Liganden.
Mechanism‐Driven Elaboration of an Enantioselective Bromocyclopropanation Reaction of Allylic Alcohols
Authors: Taillemaud Sylvain , Diercxsens Nicolas , Gagnon Alexandre , Charette André B. 
Published: September 2015

AbstractA stereoselective bromocyclopropanation of allylic alcohols using dibromomethylzinc bromide is described. Spectroscopic studies to monitor the formation of transient intermediates not only led to the development of a more‐atom‐economical halocyclopropanation reaction, but also highlighted the unique role of ether additives in the process. The desired bromo‐substituted cyclopropanes were isolated in high yields and excellent diastereo‐ as well as enantioselectivities using readily available reagents.
Nanoporous Materials Can Tune the Critical Point of a Pure Substance
Authors: Braun Efrem , Chen Joseph J. , Schnell Sondre K. , Lin Li‐Chiang , Reimer Jeffrey A. , Smit Berend 
Published: September 2015

AbstractMolecular simulations and NMR relaxometry experiments demonstrate that pure benzene or xylene confined in isoreticular metal–organic frameworks (IRMOFs) exhibit true vapor–liquid phase equilibria where the effective critical point may be reduced by tuning the structure of the MOF. Our results are consistent with vapor and liquid phases extending over many MOF unit cells. These results are counterintuitive since the MOF pore diameters are approximately the same length scale as the adsorbate molecules. As applications of these materials in catalysis, separations, and gas storage rely on the ability to tune the properties of adsorbed molecules, we anticipate that the ability to systematically control the critical point, thereby preparing spatially inhomogeneous local adsorbate densities, could add a new design tool for MOF applications.
Single Unit Cell Bismuth Tungstate Layers Realizing Robust Solar CO2 Reduction to Methanol
Authors: Liang Liang , Lei Fengcai , Gao Shan , Sun Yongfu , Jiao Xingchen , Wu Ju , Qamar Shaista , Xie Yi 
Published: September 2015

AbstractSolar CO2 reduction into hydrocarbons helps to solve the global warming and energy crisis. However, conventional semiconductors usually suffer from low photoactivity and poor photostability. Here, atomically‐thin oxide‐based semiconductors are proposed as excellent platforms to overcome this drawback. As a prototype, single‐unit‐cell Bi2WO6 layers are first synthesized by virtue of a lamellar Bi‐oleate intermediate. The single‐unit‐cell thickness allows 3‐times larger CO2 adsorption capacity and higher photoabsorption than bulk Bi2WO6. Also, the increased conductivity, verified by density functional theory calculations and temperature‐dependent resistivities, favors fast carrier transport. The carrier lifetime increased from 14.7 to 83.2 ns, revealed by time‐resolved fluorescence spectroscopy, which accounts for the improved electron‐hole separation efficacy. As a result, the single‐unit‐cell Bi2WO6 layers achieve a methanol formation rate of 75 μmol g−1 h−1, 125‐times higher than that of bulk Bi2WO6. The catalytic activity of the single‐unit‐cell layers proceeds without deactivation even after 2 days. This work will shed light on designing efficient and robust photoreduction CO2 catalysts.
A Concise and Highly Enantioselective Total Synthesis of (+)‐anti‐ and (−)‐syn‐Mefloquine Hydrochloride: Definitive Absolute Stereochemical Assignment of the Mefloquines
Authors: Rastelli Ettore J. , Coltart Don M. 
Published: September 2015

AbstractA concise asymmetric (>99:1 e.r.) total synthesis of (+)‐anti‐ and (−)‐syn‐mefloquine hydrochloride from a common intermediate is described. The key asymmetric transformation is a Sharpless dihydroxylation of an olefin that is accessed in three steps from commercially available materials. The Sharpless‐derived diol is converted into either a trans or cis epoxide, and these are subsequently converted into (+)‐anti‐ and (−)‐syn‐mefloquine, respectively. The synthetic (+)‐anti‐ and (−)‐syn‐mefloquine samples were derivatized with (S)‐(+)‐mandelic acid tert‐butyldimethylsilyl ether, and a crystal structure of each derivative was obtained. These are the first X‐ray structures for mefloquine derivatives that were obtained by coupling to a known chiral, nonracemic compound, and provide definitive confirmation of the absolute stereochemistry of (+)‐anti‐ as well as (−)‐syn‐mefloquine.
A Concise and Highly Enantioselective Total Synthesis of (+)‐anti‐ and (−)‐syn‐Mefloquine Hydrochloride: Definitive Absolute Stereochemical Assignment of the Mefloquines
Authors: Rastelli Ettore J. , Coltart Don M. 
Published: September 2015

AbstractA concise asymmetric (>99:1 e.r.) total synthesis of (+)‐anti‐ and (−)‐syn‐mefloquine hydrochloride from a common intermediate is described. The key asymmetric transformation is a Sharpless dihydroxylation of an olefin that is accessed in three steps from commercially available materials. The Sharpless‐derived diol is converted into either atransorcisepoxide, and these are subsequently converted into (+)‐anti‐ and (−)‐syn‐mefloquine, respectively. The synthetic (+)‐anti‐ and (−)‐syn‐mefloquine samples were derivatized with (S)‐(+)‐mandelic acidtert‐butyldimethylsilyl ether, and a crystal structure of each derivative was obtained. These are the first X‐ray structures for mefloquine derivatives that were obtained by coupling to a known chiral, nonracemic compound, and provide definitive confirmation of the absolute stereochemistry of (+)‐anti‐ as well as (−)‐syn‐mefloquine.
A ROS‐Activatable Agent Elicits Homologous Recombination DNA Repair and Synergizes with Pathway Compounds
Authors: Thowfeik Fathima Shazna , AbdulSalam Safnas F. , Wunderlich Mark , Wyder Michael , Greis Kenneth D. , Kadekaro Ana L. , Mulloy James C. , Merino Edward J. 
Published: September 2015

AbstractWe designed ROS‐activated cytotoxic agents (RACs) that are active against AML cancer cells. In this study, the mechanism of action and synergistic effects against cells coexpressing the AML oncogenes MLL‐AF9 fusion and FLT3‐ITD were investigated. One RAC (RAC1) had an IC50 value of 1.8±0.3 μm, with ninefold greater selectivity for transformed cells compared to untransformed cells. Treatment induced DNA strand breaks, apoptosis, and cell cycle arrest. Proteomics and transcriptomics revealed enhanced expression of the pentose phosphate pathway, DNA repair, and pathways common to cell stress. Western blotting confirmed repair by homologous recombination. Importantly, RAC1 treatment was synergistic in combination with multiple pathway‐targeting therapies in AML cells but less so in untransformed cells. Together, these results demonstrate that RAC1 can selectively target poor prognosis AML and that it does so by creating DNA double‐strand breaks that require homologous recombination.
Pd@Al2O3‐Catalyzed Hydrogenation of Allylbenzene to Propylbenzene in Methanol and Aqueous Micellar Solutions
Authors: Arbelaez Oscar , Correa Luis , Parapat Riny Yolanda , Knemeyer Kristian , Bustamante Felipe , Villa Aída Luz , Schwarze Michael 
Published: September 2015

AbstractThe palladium on alumina (Pd@Al2O3)‐catalyzed hydrogenation of allylbenzene to propylbenzene was studied in methanol and aqueous micellar solutions of sodium dodecyl sulfate (SDS), decyltrimethylammonium bromide (DTAB), and t‐octylphenoxypolyethoxyethanol (TX‐100). Over Pd@Al2O3, propylbenzene was obtained via direct hydrogenation of allylbenzene and isomerization to β‐methylstyrene which was hydrogenated afterwards. In aqueous micellar solutions, the reaction was faster than in pure water, but slower than in methanol due to lower hydrogen solubility. In the H2O/SDS system, a higher activation energy was obtained than in methanol. For the investigated surfactants, the initial reaction rate in the micellar systems decreased in the order SDS > TX‐100 > DTAB.
Highly Specific Electrochemiluminescence Detection of Cancer Cells with a Closed Bipolar Electrode
Authors: Wu Mei‐Sheng , Liu Zhen , Xu Jing‐Juan , Chen Hong‐Yuan 
Published: September 2015

AbstractAn advanced biosensor based on a closed bipolar electrode (BPE)–electrochemiluminescence (ECL) strategy is proposed for cancer cell adhesion, specific recognition, and detection with dual biomarkers. The system consists of a two‐channel polydimethylsiloxane (PDMS) chip (sensing channel and reporting channel) connected through a U‐shaped indium tin oxide BPE at a glass surface. A sandwich‐type cancer cell detection model is developed at the cathode of the BPE with two recognition molecules, folic acid (FA) and an aptamer. On the basis of the high affinity between FA and the folate receptor that is overexpressed at a cancer cell membrane as well as the excellent conductivity of graphene–Au conjugates, this strategy could achieve the sensitive detection of HL‐60 cells, with a limit as low as 18 cells in 30 μL of cell suspension. Control experiments confirm that the sandwich assay specifically captures cancer cells and recognizes target cells.
Experimental and Computational Evidence of Highly Active Fe Impurity Sites on the Surface of Oxidized Au for the Electrocatalytic Oxidation of Water in Basic Media
Authors: Klaus Shannon , Trotochaud Lena , Cheng Mu‐Jeng , Head‐Gordon Martin , Bell Alexis T. 
Published: September 2015

AbstractAddition of Fe to Ni‐ and Co‐based (oxy)hydroxides has been shown to enhance the activity of these materials for electrochemical oxygen evolution. Here we show that Fe cations bound to the surface of oxidized Au exhibit enhanced oxygen evolution reaction (OER) activity. We find that the OER activity increases with increasing surface concentration of Fe. Density functional theory analysis of the OER energetics reveals that oxygen evolution over Fe cations bound to a hydroxyl‐terminated oxidized Au (Fe–Au2O3) occurs at an overpotential ∼0.3 V lower than over hydroxylated Au2O3(0.82 V). This finding agrees well with experimental observations and is a consequence of the more optimal binding energetics of OER reaction intermediates at Fe cations bound to the surface of Au2O3. These findings suggest that the enhanced OER activity reported recently upon low‐potential cycling of Au may be due to surface Fe impurities rather than to “superactive” AuIIIsurfaquo species.
Self‐Assembly of Tetraphenylalanine Peptides
Authors: Mayans Enric , Ballano Gema , Casanovas Jordi , Díaz Angélica , Pérez‐Madrigal Maria M. , Estrany Francesc , Puiggalí Jordi , Cativiela Carlos , Alemán Carlos 
Published: September 2015

AbstractThree different tetraphenylalanine (FFFF) based peptides that differ at the N‐ and C‐termini have been synthesized by using standard procedures to study their ability to form different nanoassemblies under a variety of conditions. The FFFF peptide assembles into nanotubes that show more structural imperfections at the surface than those formed by the diphenylalanine (FF) peptide under the same conditions. Periodic DFT calculations (M06L functional) were used to propose a model that consists of three FFFF molecules defining a ring through head‐to‐tail NH3+⋅⋅⋅−OOC interactions, which in turn stack to produce deformed channels with internal diameters between 12 and 16 Å. Depending on the experimental conditions used for the peptide incubation, N‐fluorenylmethoxycarbonyl (Fmoc) protected FFFF self‐assembles into a variety of polymorphs: ultra‐thin nanoplates, fibrils, and star‐like submicrometric aggregates. DFT calculations indicate that Fmoc‐FFFF prefers a parallel rather than an antiparallel β‐sheet assembly. Finally, coexisting multiple assemblies (up to three) were observed for Fmoc‐FFFF‐OBzl (OBzl = benzyl ester), which incorporates aromatic protecting groups at the two peptide terminals. This unusual and noticeable feature is attributed to the fact that the assemblies obtained by combining the Fmoc and OBzl groups contained in the peptide are isoenergetic.
Decanuclear Ln10 Wheels and Vertex‐Shared Spirocyclic Ln5 Cores: Synthesis, Structure, SMM Behavior, and MCE Properties
Authors: Das Sourav , Dey Atanu , Kundu Subrata , Biswas Sourav , Narayanan Ramakirushnan Suriya , Titos‐Padilla Silvia , Lorusso Giulia , Evangelisti Marco , Colacio Enrique , Chandrasekhar Vadapalli 
Published: September 2015

AbstractThe reaction of a Schiff base ligand (LH3) with lanthanide salts, pivalic acid and triethylamine in 1:1:1:3 and 4:5:8:20 stoichiometric ratios results in the formation of decanuclear Ln10 (Ln=Dy(1), Tb(2), and Gd (3)) and pentanuclear Ln5 complexes (Ln=Gd (4), Tb (5), and Dy (6)), respectively. The formation of Ln10 and Ln5 complexes are fully governed by the stoichiometry of the reagents used. Detailed magnetic studies on these complexes (1–6) have been carried out. Complex 1 shows a SMM behavior with an effective energy barrier for the reversal of the magnetization (Ueff)=16.12(8) K and relaxation time (τo)=3.3×10−5 s under 4000 Oe direct current (dc) field. Complex 6 shows the frequency dependent maxima in the out‐of‐phase signal under zero dc field, without achieving maxima above 2 K. Complexes 3 and 4 show a large magnetocaloric effect with the following characteristic values: −ΔSm=26.6 J kg−1 K−1 at T=2.2 K for 3 and −ΔSm=27.1 J kg−1 K−1 at T=2.4 K for 4, both for an applied field change of 7 T.
Transfer of Copper from an Amyloid to a Natural Copper‐Carrier Peptide with a Specific Mediating Ligand
Authors: Nguyen Michel , Bijani Christian , Martins Nathalie , Meunier Bernard , Robert Anne 
Published: September 2015

AbstractThe oxidative stress that arises from the catalytic reduction of dioxygen by CuII/I‐loaded amyloids is the major pathway for neuron death that occurs in Alzheimer’s disease. In this work, we show that bis‐8(aminoquinoline) ligands, copper(II) specific chelators, are able to catalytically extract CuII from Cu–Aβ1–16 and then completely release CuI in the presence of glutathione to provide a CuI–glutathione complex, a biological intermediate that is able to deliver copper to apo forms of copper–protein complexes. These data demonstrate that bis‐8(aminoquinolines) can perform the transfer of copper ions from the pathological Cu–amyloid complexes to regular copper–protein complexes. These copper‐specific ligands assist GSH to recycle CuI in an AD brain and consequently slow down oxidative damage that is due to copper dysregulation in Alzheimer’s disease. Under the same conditions, we have shown that the copper complex of PBT2, a mono(8‐hydroxyquinoline) previously used as a drug candidate, does not efficiently release copper in the presence of GSH. In addition, we report that GSH itself was unable to fully abstract copper ions from Cu–β‐amyloid complexes.
Synthesis of Phenylene Vinylene Macrocycles through Acyclic Diene Metathesis Macrocyclization and Their Aggregation Behavior
Authors: Zhang Chenxi , Yu Chao , Long Hai , Denman Ryan J. , Jin Yinghua , Zhang Wei 
Published: September 2015

AbstractA series of phenylene vinylene macrocycles (PVMs) bearing substituents with various sizes and electronic properties have been synthesized through a one‐step acyclic diene metathesis macrocyclization approach and their aggregation behaviors have been investigated. In great contrast to the aggregation of the analogous phenylene ethynylene macrocycles, which aggregate only when substituted with electron‐withdrawing groups, these PVMs undergo exceptionally strong aggregation, regardless of the electron‐donating or ‐withdrawing characters of the substituents. The unusual aggregation behavior of the PVMs is further investigated with thermodynamic and computer modeling studies, which show a good agreement with the recently proposed direct through‐space interaction model, rather than the polar/π model. The high aggregation tendency of PVMs suggests the great potential of this novel class of shape‐persistent macrocycles in a variety of applications, such as ion channels, host–guest recognition, and catalysis.
Fluorescence Polarization Based Nucleic Acid Testing for Rapid and Cost‐Effective Diagnosis of Infectious Disease
Authors: Park Ki Soo , Charles Richelle C. , Ryan Edward T. , Weissleder Ralph , Lee Hakho 
Published: September 2015

AbstractA new nucleic acid detection method was developed for a rapid and cost‐effective diagnosis of infectious disease. This approach relies on the three unique elements: 1) detection probes that regulate DNA polymerase activity in response to the complementary target DNA; 2) universal reporters conjugated with a single fluorophore; and 3) fluorescence polarization (FP) detection. As a proof‐of‐concept, the assay was used to detect and sub‐type Salmonella bacteria with sensitivities down to a single bacterium in less than three hours.
Cobalt(III)‐Catalyzed CH/NO Functionalizations: Isohypsic Access to Isoquinolines
Authors: Wang Hui , Koeller Julian , Liu Weiping , Ackermann Lutz 
Published: September 2015

AbstractCH/NO functionalizations by cobalt(III) catalysis allowed the expedient synthesis of a broad range of isoquinolines. Thus, internal and challenging terminal alkynes proved to be viable substrates for an isohypsic annulation, which was shown to proceed by a facile CH cobaltation.
Synthesis, Structural Characterization, and Chiroptical Studies of Bidentate Salen‐Type Lanthanide (III) Complexes
Authors: Berardozzi Roberto , Pescitelli Gennaro , Di Pietro Sebastiano , Resta Claudio , Ballistreri Francesco P. , Pappalardo Andrea , Tomaselli Gaetano A. , Di Bari Lorenzo 
Published: September 2015

AbstractThe salen‐type ligand prepared with (R,R) diphenylethan‐1,2‐diamine and salicylaldehyde provides stable and inert complexes KLnL2 upon simple reaction with lanthanide halides or pseudohalides LnX3 (Ln = Tb3+‐Lu3+; X = Cl− or TfO−) of its potassium salt. All the complexes were completely characterized through nuclear magnetic resonance (NMR), electronic circular dichroism (ECD) in the UV and some (Er3+, Tm3+, Yb3+) also with Near‐IR ECD (NIR‐ECD) and luminescence (Tb3+, Tm3+). Careful analysis of the NMR shifts demonstrated that the complexes are isostructural in solution and afforded an accurate geometry. This was further confirmed by means of Density Functional Theory (DFT) optimization of the Lu3+ complex, and by comparing the ligand‐centered experimental and time‐dependent TD‐DFT computed UV‐ECD spectra. As final validation, we used the NIR‐ECD spectrum of the Yb3+ derivative calculated by means of Richardson's equations. The excellent match between calculated and experimental ECD spectra confirm the quality of the NMR structure. Chirality 27:857–863, 2015. © 2015 Wiley Periodicals, Inc.