bluuebunny/crossref_metadata_2025_split huggingface dataset:
From Monodisperse Thienyl‐ and Furylborane Oligomers to Polymers: Modulating the Optical Properties through the Hetarene Ratio
Authors: Lik Artur , Jenthra Sangeth , Fritze Lars , Müller Lars , Truong Khai‐Nghi , Helten Holger 
Published: March 2018

AbstractThe application of our newly developed B–C coupling method by catalytic Si/B exchange is demonstrated for the synthesis of a series of triarylboranes (1), monodisperse thienyl‐ and furylborane dimers (2) and trimers (9), extended oligomers (3) and polymers (3′), as well as mixed (oligo)thienyl‐/furylboranes. The structures of 1 aaTip, 1 bbTip, and 2 bbbMes*, determined by X‐ray crystallography, reveal largely coplanar hetarene rings and BR3 environments, which are most pronounced in the furylborane species. Photophysical investigations, supported by TD‐DFT calculations, revealed pronounced π‐electron delocalization over the hetarene backbones including the boron centers. With an extended series of derivatives of varying chain lengths available, we were able to determine the effective conjugation lengths (ECL) of poly(thienylborane)s and poly(furylborane)s, which have been reached with the highest‐molecular‐weight derivatives of our study. Through variation of the furan‐to‐thiophene ratio, the photophysical properties of these materials are effectively modulated. Significantly, higher furan contents lead to considerably increased fluorescence intensities. Compounds 1 aaTip, 1 bbTip, and 3 aTip showed the ability to bind fluoride anions. The binding process is signaled by a distinct change in their optical absorption characteristics, thus rendering these materials attractive targets for sensory applications.
Access to 3‐Oxindoles from Allylic Alcohols and Indoles
Authors: Lauwick Hortense , Sun Yang , Akdas‐Kilig Huriye , Dérien Sylvie , Achard Mathieu 
Published: March 2018

AbstractThe site‐selective and regioselective allylation of 2‐substituted indoles was performed by using a ruthenium(IV) precatalyst containing a phosphine–sulfonate chelate. Mono‐, di‐, and triallylated indoles were selectively obtained depending on the reaction conditions with the formation of water as the only byproduct. The preparation of 3‐oxindole derivatives was then successfully performed owing to air oxidation of the corresponding allylated indoles. Diallylated pseudoindoxyls were proven to be good synthons to perform cyclization through a ring‐closing metathesis reaction to afford the corresponding tricyclic adducts. The photophysical properties of the 3‐oxindoles were measured, and some of the compounds showed strong fluorescence in water.
Heterogeneous Pyrophosphate‐Linked DNA–Oligonucleotides: Aversion to DNA but Affinity for RNA
Authors: Anderson Brooke A. , Krishnamurthy Ramanarayanan 
Published: March 2018

AbstractPyrophosphate linkages are important in extant biology and are hypothesized to have played a role in prebiotic chemistry and in the origination of oligonucleotides. Inspired by pyrophosphate as backbones of primordial oligomers, DNA oligomers with varying amounts of pyrophosphate inserts (ppDNA) were synthesized and investigated for their base‐pairing properties. As expected, pyrophosphate inserts into the backbone compromised the thermal stability of ppDNA–DNA duplexes. In contrast, the ppDNA–RNA duplex exhibited, remarkably, duplex stability, even with accumulation of pyrophosphate linkages. This seems to be a consequence of an increase in the diameter of the double‐helix with eight‐bond‐repeat units, and higher inclination of the base‐pair axis with respect to the backbone in RNA (A‐form), compared with that in DNA (B‐form). These results suggest that pyrophosphate‐linked oligonucleotides could harbor functional capabilities with implications for their roles in the origins of life and chemical biology.
Hydrodynamic analysis of gas‐liquid‐liquid‐solid reactors using the XDEM numerical approach
Authors: Baniasadi Maryam , Peters Bernhard , Baniasadi Mehdi , Besseron Xavier 
Published: March 2018

AbstractMultiphase reactors are abundantly used in many industries. Among them, few reactors deal with four phases called gas‐liquid‐liquid‐solid systems, which receive less attention due to their complex situation. Numerical study of such complex systems is not easy and requires large computational effort. In this study, a discrete‐continuous numerical model known as the eXtended discrete element method (XDEM) is proposed to investigate the hydrodynamic behaviour of fluid phases passing through the packed bed of solid particles. This model is applied to the dripping zone of a blast furnace. In this zone, two distinct liquid phases, namely liquid iron and slag, flow through a pile of coke particles while exchanging momentum. In this work, besides the solid‐fluid and gas‐liquid interactions, the liquid‐liquid interactions are also studied and the phases’ mutual effects are discussed. In addition, a sensitivity study on the slag viscosity is performed, which shows the importance of liquid phase properties on the system behaviour. The results evaluation shows that the liquid iron accelerates the downward flow of the slag and the slag decelerates the downward flow of the liquid iron phase due to the resistance force caused by their relative velocity.
Lactonization of C(sp2)—H Bonds in Enamides with CO2
Authors: Zhang Zhen , Zhu Chun‐Jun , Miao Meng , Han Jie‐Lian , Ju Tao , Song Lei , Ye Jian‐Heng , Li Jing , Yu Da‐Gang 
Published: March 2018

AbstractHerein, we report a novel synthesis of 1,3‐oxazin‐6‐ones from enamides with CO2 through C—H carboxylation and one‐pot cyclization. This transition‐metal‐free and redox‐neutral process features broad substrate scope, good functional group tolerance and facile product derivatization. The nucleophilic attack to CO2 from the electron‐rich alkene is demonstrated for this reaction.
Head and neck squamous cell cancers in the United States are rare and the risk now is higher among white individuals compared with black individuals
Authors: Fakhry Carole , Krapcho Martin , Eisele David W. , D'Souza Gypsyamber 
Published: March 2018

BACKGROUNDThe increasing incidence of oropharyngeal squamous cell cancer (OPSCC) is well established. However, up‐to‐date incidence estimates and trends for head and neck squamous cell cancers (HNSCCs) overall, including major anatomic sites, and nonoropharyngeal (non‐OP) HNSCCs by sex, race, and age in the United States are not well described.METHODSA retrospective analysis of incident HNSCCs during 1992 through 2014 using the Surveillance, Epidemiology, and End Results database was performed to evaluate the incidence of HNSCCs overall, OPSCC, and non‐OP HNSCC (those of the larynx, oral cavity, hypopharynx, nasopharynx, and nasal cavity). Incidence rates were calculated overall and by subgroups of interest, and incidence rate ratios were used to compare rates between groups. The incidence rates presented were per 100,000 population and were age adjusted to the 2000 US standard population (19 age groups; Census P25‐1130). The annual percent change (APC) was modeled with and without joinpoints.RESULTSThe incidence of HNSCC overall declined (average APC [aAPC], ‐0.8; P<.001) despite significant increases in the incidence of OPSCCs, most notably between 2000 and 2014 (APC, 2.1; P<.001). Significant declines in incidence were observed for all non‐OP HNSCC sites for both women and men (P<.001 each). Among women, the risk of OPSCC also significantly decreased (aAPC, ‐0.8; P = .002), whereas the risk among men was stable during 1992 through 2001 (APC, 0.4; P = .42) and then significantly increased from 2001 to 2014 (APC, 2.7; P<.001). Decreases in the risk of non‐OP HNSCC were especially large for black women (aAPC, ‐2.6; P<.001) and men (aAPC, ‐3.0; P<.001). Although the incidence of HNSCC previously was highest among black individuals, since 2009 its incidence has been higher among white compared with black individuals.CONCLUSIONSThe incidence of HNSCC is declining, especially for non‐OP HNSCC and among black individuals. Cancer 2018;124:2125‐33. © 2018 American Cancer Society.
Photo and Thermo Dual‐Responsive Copolymer Surfaces for Efficient Cell Capture and Release
Authors: Hao Yuwei , Liu Hongliang , Li Guannan , Cui Haijun , Jiang Lei , Wang Shutao 
Published: March 2018

AbstractTo overcome the low efficiency of single‐responsive smart surfaces, we have constructed a dual‐responsive smart surface – poly(spiropyran‐co‐N‐isopropylacrylamide) (poly(SP‐co‐NiPAAm))‐grafted silicon nanowire arrays – by combining photo‐responsive SP and thermo‐responsive NiPAAm units for enhancing the efficiencies of cancer‐cell capture and release. These enhanced efficiencies probably originate from the binary cooperative effect of two responsive building units: NiPAAm units can decrease the steric hindrance between SP units during the isomerization while SP units can facilitate phase transition of NiPAAm units. This study provides a new strategy for designing smart materials and surfaces with efficient responsiveness for biomedical applications.
Thermodynamic Calculations to Determine the Optimal Composition of Oxide Catalysts
Authors: Gushchin Pavel A. , Lyubimenko Valentina A. , Ivanov Evgenii V. , Kolesnikov Sergey I. , Petrova Daria A. , Vinokurov Vladimir A. , Kolesnikov Ivan M. 
Published: March 2018

AbstractThermodynamic calculations of the optimal compositions of oxide catalysts with different natures are performed based on the theory of catalysis by polyhedra. The obtained compositions of the active catalysts agree with experimental data. The electrostatic potential generated by polyhedra of metal‐oxide catalysts in a variety of directions is calculated. The dependence of the sign and magnitude of the potential on the distance from the central metal ion towards the vertex of the polyhedron, the middle of its edge or the centre of the face is estimated. It is assumed that the magnitude of the potential can serve as a reference point for determining active centres, which produce adsorption complexes and intermediate compounds.
Carbon Monoxide Hydrogenation on Ice Surfaces
Authors: Kuwahata Kazuaki , Ohno Kaoru 
Published: March 2018

AbstractWe have performed density functional calculations to investigate the carbon monoxide hydrogenation reaction (H+CO→HCO), which is important in interstellar clouds. We found that the activation energy of the reaction on amorphous ice is lower than that on crystalline ice. In the course of this study, we demonstrated that it is roughly possible to use the excitation energy of the reactant molecule (CO) in place of the activation energy. This relationship holds also for small water clusters at the CCSD level of calculation and the two‐layer‐level ONIOM (CCSD : X3LYP) calculation. Generally, since it is computationally demanding to estimate activation energies of chemical reactions in a circumstance of many water molecules, this relationship enables one to determine the activation energy of this reaction on ice surfaces from the knowledge of the excitation energy of CO only. Incorporating quantum‐tunneling effects, we discuss the reaction rate on ice surfaces. Our estimate that the reaction rate on amorphous ice is almost twice as large as that on crystalline ice is qualitatively consistent with the experimental evidence reported by Hidaka et al. [Chem. Phys. Lett., 2008, 456, 36.]
One‐Pot Soft‐Template Synthesis of Nanostructured Copper‐Supported Mesoporous Carbon FDU‐15 Electrocatalysts for Efficient CO2 Reduction
Authors: Şahin Nihat Ege , Comminges Clément , Le Valant Anthony , Kiener Julien , Parmentier Julien , Napporn Teko W. , Melinte Georgian , Ersen Ovidiu , Kokoh Kouakou B. 
Published: March 2018

AbstractCopper‐supported mesoporous carbon nanocatalysts (Cu/FDU‐15) were synthesized using an easy and convenient one‐pot soft‐template method for low‐overvoltage CO2 electroreduction. TEM imaging revealed the presence of large Cu nanoparticles (diameter 140 nm) with Cu2O nanoparticles (16 nm) as an additional phase. From the electron tomography observations, we found that the copper particles were placed inside and on the exterior surface of the porous FDU‐15 support, providing an accessible surface for electrocatalytic reactions. CO2 electrolyses showed that the mesostructured Cu/FDU‐15‐350 cathode materials were active towards CO2 conversion to formic acid with 22 % Faradaic efficiency at a remarkably low overpotential of 290 mV, hydrogen being the only side‐product. The catalyst's activity correlates to the calculated metallic surface area, as determined from a geometrical model, confirming that the mesoporous channels act as a diffusion path for the CO2 molecule, and that the whole Cu surface is accessible to CO2, even if particles are entrapped in the carbon matrix.
Reactivity of CO and C2H4 on Bimetallic PtxAg1‐x/Pt(111) Surface Alloys Investigated by High‐Resolution X‐ray Photoelectron Spectroscopy
Authors: Bauer Udo , Späth Florian , Düll Fabian , Bachmann Phillip , Steinhauer Johann , Steinrück Hans‐Peter , Papp Christian 
Published: March 2018

AbstractWe have investigated the adsorption and thermal reactivity of CO and C2H4 on well‐defined bimetallic PtxAg1‐x/Pt(111) surface alloys (with x=0.67, 0.50, 0.38 and 0.32) using in situ synchrotron‐based high‐resolution X‐ray photoelectron spectroscopy. During low‐temperature (140 K) adsorption of CO, we find population of the energetically more stable Pt on‐top site followed by the Pt bridge site, as known from clean Pt(111); CO does not adsorb on Ag facets under the applied conditions. The total CO coverage linearly decreases with Ag surface content. Upon heating, COon‐top and CObridge desorb at higher temperatures than on bare Pt(111), for example, by ∼65 K for COon‐top for an Ag content of 33 %. This shift is due to the well‐known electronic ligand‐effect of Ag atoms surrounding Pt atoms/clusters. For C2H4 adsorption on the AgPt alloys at low temperature (120 K), we find two species in the C1s XP spectrum, each displaying a vibrational fine structure; this contrasts the situation on clean Pt(111), where only one species is found. Upon heating, ethylene reacts with ethylidyne being the dominant intermediate; in contrast to clean Pt(111), on the alloy surfaces the reaction to CCH3 occurs at much lower temperatures, e. g. by ∼60 K for the alloy with 68 % Ag, and no ethylene desorption is found.
Periodic Grating‐like Patterns Induced by Self‐Assembly of Gelator Fibres in Nematic Gels
Authors: Topnani Neha B. , Prutha N. , Pratibha R. 
Published: March 2018

AbstractPeriodic orientation patterns occurring in nematic gels, revealed by optical and scanning electron microscopy, are found to be formed by spontaneous self‐assembly of fibrous aggregates of a low‐molecular‐weight organogelator in an aligned thermotropic liquid crystal (LC). Self‐organization into periodic structures is also reflected in a calorimetric study, which shows the occurrence of three thermoreversible states, namely, isotropic liquid, nematic and nematic gel. The segregation and self‐assembly of the fibrous aggregates leading to pattern formation are attributed to the highly polar LC and to hydrogen bonding between gelator molecules, as shown by X‐ray diffraction and vibrational spectroscopy. This study aims to investigate in detail the effect of the chemical nature and alignment of an anisotropic solvent on the morphology of the gelator fibres and the resulting gelation process. The periodic organization of LC‐rich and fibre‐rich regions can also provide a way to obtain templates for positioning nanoparticle arrays in an LC matrix, which can lead to novel devices.
The Antagonist Effect of Nitrogen Lone Pair: 3JHFversus5JHF
Authors: Barbosa Thaís M. , Viesser Renan V. , Martins Lucas G. , Rittner Roberto , Tormena Cláudio F. 
Published: March 2018

AbstractThe long‐range scalar coupling constant between proton and fluorine nuclei, 5JHF, is observed to be larger than 3JHF in the pyrimidinyl moiety of voriconazole. A set of smaller molecules is chosen (fluorobenzene, N‐methyl‐2‐fluoropyridine, N‐methyl‐3‐fluoropyridine, 3‐fluoropyridine, 5‐pyrimidine, and 2‐fluoropyridine) to evaluate the influence of the nitrogen atom in the experimental JHF values. Spectral aliased pure shift heteronuclear single quantum coherence spectroscopy (SAPS‐HSQC) is applied to determine the relative sign between the JCF and JHF scalar couplings. Theoretical calculations show that the 3JHF and 5JHF coupling constants can be described mainly by a Fermi contact (FC) transmission mechanism. A decomposition analysis of JHF in terms of localized molecular orbital (LMO) contributions allows us to determine that the interaction involving the nitrogen lone pair (LPN) is the main reason for the larger 5JHF compared to 3JHF. Our analysis indicates that delocalization of LPN has a positive contribution to the long‐range coupling, while a negative one is observed for 3JHF.
Molecular Modelling of the H2‐Adsorptive Properties of Tetrazolate‐Based Metal−Organic Frameworks: From the Cluster Approach to Periodic Simulations
Authors: Brea Oriana , Luna Alberto , Díaz Cristina , Corral Inés 
Published: March 2018

AbstractHydrogen has been proposed as a long‐term non‐fossil fuel to be used in a future ideal carbon‐neutral energetic economy. However, its low volumetric energy density hinders its storage and transportation. Metal−organic frameworks (MOFs) represent very promising materials for this purpose due to their very extended surface areas. Azolates, in particular tetrazolates, are – together with carboxylate functionalities – very common organic linkers connecting metallic secondary building units in MOFs. This study addresses, from a theoretical perspective, the H2 adsorptive properties of tetrazolate linkers at the molecular level, following a size‐progressive approach. Specifically, we have investigated how the physisorption energies and geometries are affected when changing the environment of the linker by considering the azolates in the gas phase, immersed in a finite cluster, or being part of an infinite extended crystal material. Furthermore, we also study the H2 adsorptive capacity of these linkers within the cluster model.
Localizing Conformational Hinges by NMR: Where Do Hepatitis B Virus Core Proteins Adapt for Capsid Assembly?
Authors: Lecoq Lauriane , Wang Shishan , Wiegand Thomas , Bressanelli Stéphane , Nassal Michael , Meier Beat H. , Böckmann Anja 
Published: March 2018

AbstractThe hepatitis B virus (HBV) icosahedral nucleocapsid is assembled from 240 chemically identical core protein molecules and, structurally, comprises four groups of symmetrically nonequivalent subunits. We show here that this asymmetry is reflected in solid‐state NMR spectra of the capsids, in which peak splitting is observed for a subset of residues. We compare this information to dihedral angle variations from available 3D structures and also to computational predictions of “dynamic” domains and molecular hinges. We find that although, at the given resolution, dihedral angles variations directly obtained from the X‐ray structures are not precise enough to be interpreted, the chemical‐shift information from NMR correlates, and interestingly goes beyond, information from bioinformatics approaches. Our study reveals the high sensitivity with which NMR can detect the residues allowing the subtle conformational adaptations needed in lattice formation. Our findings are important for understanding the formation and modulation of protein assemblies in general.
Crystal Size Distribution Resulting from the Time Dependence of Crystal Nucleation
Authors: Nanev Christo N. 
Published: March 2018

AbstractMost of the experimental studies show that new‐phase nucleation runs over prolonged time periods rather than instantaneously. After crystals nucleate, they start growing immediately. Therefore, the earlier a crystal nucleates, the larger it grows. This instigates a definite crystal size distribution (CSD). The resulting (from the initial crystal growth during the nucleation stage) CSD is calculated from the logistic time dependence of crystal number density. Having the shape of an ogee curve, CSD remains practically unchanged during the following crystal growth stage until the onset of Ostwald ripening. Only earlier born (and hence larger) crystals survive during the Ostwald ripening; the smallest crystals, which are the last born species, are dissolved. As far as the logistic dependence of crystal nuclei number density vs. nucleation time explains small molecule and protein crystallization, the calculated CSD should also describe crystallization of both small and large bio‐molecules.
The social reputation of European companies: Does anti‐corruption disclosure affect stakeholders' perceptions?
Authors: Álvarez Etxeberria Igor , Aldaz Odriozola Maider 
Published: March 2018

AbstractCorruption is a very important topic in society but also for businesses. However, there are few empirical studies that analyze corruption from the point of view of disclosure by companies and none that analyze its effect in corporate reputation. The aim of this paper is to use stakeholder theory to analyze the potential power of reporting in influencing stakeholders' perceptions and communication tools, such as sustainability reports, to bolster corporate reputation in relation to the social issue of corruption. Based on a regression analysis using data from the 70 largest European companies, we find that disclosure positively correlates with social reputation in the anti‐corruption area. The study addresses a gap in the literature by highlighting the fact that this global and key social issue has not yet been analyzed empirically.
Environmental reporting policy and corporate structures: An international analysis
Authors: Pucheta‐Martínez María Consuelo , Gallego‐Álvarez Isabel 
Published: March 2018

AbstractThe corporate governance structures of firms differ among countries for cultural, political or social reasons, among others, which may affect the environmental reporting policies of firms. In this regard, institutional contexts where firms are domiciled vary among regions, and consequently environmental reporting policies of firms will depend on the institutional factors where companies operate. The aim of this paper is to examine how institutional features such as investor protection, ownership dispersion and market‐oriented financial systems impact on environmental reporting policies of firms in different countries. The sample is composed of 5293 international companies, whose information was obtained from the Thomson Reuters Eikon database for the year 2015. The theoretical framework is based on institutional and stakeholder theories. Institutional theory argues that companies localized in the same institutional setting tend to behave in similar ways, and therefore the stakeholders’ attitudes toward environmental reporting will be similar. The findings report that companies operating in countries with high ownership dispersion and where the most important capital providers are capital markets are most likely to disclose environmental issues, while firms domiciled in countries with strong investor protection are not associated with environmental disclosure policies.