bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalytic Asymmetric Huisgen Alkyne–Azide Cycloaddition of Bisalkynes by Copper(I) Nanoparticles
Authors: Chen Mu‐Yi , Xu Zheng , Chen Li , Song Tao , Zheng Zhan‐Jiang , Cao Jian , Cui Yu‐Ming , Xu Li‐Wen 
Published: September 2017

AbstractThe use of chiral ligands to tune the reactivity and enantioselectivity of transition‐metal catalyst for asymmetric transformations is a central challenge in synthetic organic chemistry. In this manuscript, chiral P‐ligand (Tao‐Phos)‐assisted Cu2O‐nanoparticles‐catalyzed asymmetric azide–alkyne Huisgen cycloaddition is reported. The unique features of Tao‐Phos were determined in the copper‐catalyzed desymmetrization of pyrazolone‐derived bisalkynes through catalytic asymmetric Huisgen [3+2] cycloaddition (CAHC). This CAHC transformation resulted in good yields with moderate to high enantioselectivities.
Coupling and Dearomatization of Pyridines at a Transient η2‐Cyclopropene/Bicyclobutane Zirconocene Complex
Authors: Romero Nuria , Dufrois Quentin , Vendier Laure , Dinoi Chiara , Etienne Michel 
Published: September 2017

AbstractThis paper reports on stereospecific coupling reactions between an η2‐cyclopropene ligand and pyridine derivatives, which are preferred to alternative C−H bond activation reactions. The dicyclopropylzirconocene complex [Cp2Zr(c‐C3H5)2] (1) eliminates cyclopropane to generate the η2‐cyclopropene/bicyclobutane intermediate [Cp2Zr(η2‐c‐C3H4)] (A). A does not activate any pyridine C−H bonds, but rather pyridine inserts into a Zr−C bond of A, yielding an azazirconacycle with a dearomatized pyridyl group [Cp2Zr{κ2‐N,C8‐(2‐c‐C3H4)‐C5H5N}] (2). Kinetic data, isotopelabelling experiments, and DFT calculations indicate that the rate‐determining step of this stereospecific reaction is cyclopropane elimination, and that the stability of the intermediate [Cp2Zr(η2‐c‐C3H4)(NC5H5)] (A‐py) governs the selectivity of the reaction. Complex 2 tautomerizes to [Cp2Zr{κ2‐N,C8‐(2‐C3H5)‐C5H4N}] (6) through a base‐catalyzed proton migration accompanied by cyclopropyl opening and restoration of conjugation within the zirconacycle.
Strategy for Stereoselective Metal‐free α‐Functionalization of 2‐Azaaryl Acetates with N‐Boc Imines
Authors: Bastida Iñaki , Segundo Marcos San , López Rosa , Palomo Claudio 
Published: September 2017

AbstractWe report the first diastereo‐ and enantioselective formal Mannich reaction of 2‐pyridyl acetates which gives rise to α‐ and β‐functionalized 2‐substituted pyridines. Key for success is the previous azaarene N‐oxide formation enabling α‐carbon deprotonation by a mild bifunctional Brønsted base and subsequent reaction with N‐Boc imines under almost perfect stereocontrol.
Flow Enhancement of Shear‐Thinning Liquids in Capillaries Subjected to Longitudinal Vibrations
Authors: Ellenberger Jürg , Krishna Rajamani 
Published: September 2017

AbstractApplication of sinusoidal vibrations in the longitudinal direction causes a significant enhancement in the flow rate of shear‐thinning carboxymethylcellulose and polyacrylamide solutions inside capillaries. Depending on the vibration frequency and amplitude, flow enhancements of up to a factor of 9.6 have been realized. Video imaging of a tracer particle inside the tube provides insights into the liquid motion. In particular, it should be noted that the phase shift between the sinusoidal motion of the tube wall and the liquid inside the tube is of high importance in determining the flow enhancement factor.
Titania‐Supported Single‐Atom Platinum Catalyst for Water‐Gas Shift Reaction
Authors: Ammal Salai Cheettu , Heyden Andreas 
Published: September 2017

AbstractDensity functional theory (DFT) and microkinetic modeling are used to examine the water‐gas shift (WGS) reaction on TiO2(110)‐supported single Pt atoms. A CO‐adsorbed Pt atom supported on a TiO2 surface exhibits a lower activity for the WGS than the Pt2+ ion supported on a doped TiO2 surface, although DFT predicts the CO‐adsorbed Pt on an undoped TiO2 surface to be thermodynamically more stable. Trends observed in WGS activity for different active sites of TiO2‐supported Pt catalysts can be explained in terms of CO adsorption strength and the ability to form an oxygen vacancy on the oxide support.
Basic Properties of Nd‐Doped GYSGG Laser Crystal
Authors: Ding Shoujun , Zhang Qingli , Luo Jianqiao , Liu Wenpeng , Sun Dunlu , Wang Xiaofei , Sun Guihua , Gao Jinyun 
Published: September 2017

AbstractIn the present work, we investigated the mechanical properties (including hardness, fracture toughness, brittleness index and yield strength) of Nd0.03Gd0.93Y2.04Sc2Ga3O12 (Nd:GYSGG) laser crystal using Vickers microhardness tester, for the first time. The defects morphology of Nd:GYSGG crystal were investigated by using chemical etching method with phosphoric acid etchant. The absorption spectrum of Nd:GYSGG from 300 to 2800 nm was measured at room temperature and the absorption peaks were assigned. The fluorescence lifetime of the 4F3/2→4I11/2 transition of Nd3+ in GYSGG is fitted to be 221.3 μs. The three Judd‐Ofelt intense parameters Ω2, 4, 6 were calculated to be 0.329 × 10−20 cm2, 2.761 × 10−20 cm2 and 4.222 × 10−20 cm2, respectively. All these demonstrate that Nd:GYSGG crystal is a good candidate laser material.
Effect of Formamidinium/Cesium Substitution and PbI2 on the Long‐Term Stability of Triple‐Cation Perovskites
Authors: Shukla Shashwat , Shukla Sudhanshu , Haur Lew Jia , Dintakurti Sai S. H. , Han Guifang , Priyadarshi Anish , Baikie Tom , Mhaisalkar Subodh G. , Mathews Nripan 
Published: September 2017

AbstractAltering cation and anion ratios in perovskites has proven an excellent means of tuning the perovskite properties and enhancing the performance. Recently, methylammonium/formamidinium/cesium triple‐cation mixed‐halide perovskites have demonstrated efficiencies up to 22 %. Similar to the widely explored methylammonium lead halide, excess PbI2 is added to these perovskite films to enhance their performances. The excess PbI2 is known to be beneficial for the performance. However, its impact on stability is less well known. Triple‐cation perovskites deploy excess PbI2 up to 8 %. Thus, it is imperative to analyze the role of excess PbI2 in the degradation kinetics. In this study, the amount of PbI2 in the triple‐cation perovskite films is varied and the degradation kinetics monitored by X‐ray diffraction and optical absorption spectroscopy. The inclusion of excess PbI2 is shown to adversely affect the stability of the material. Faster degradation kinetics are observed for samples with higher PbI2 contents. However, samples with excess PbI2 also showed superior properties such as enhanced grain sizes and better optical absorption. Thus, careful management of the PbI2 quantity is required to obtain better stability and alternative pathways should be explored to achieve better device performance rather than adding excess PbI2.
Cascade Reductive Etherification of Bioderived Aldehydes over Zr‐Based Catalysts
Authors: Shinde Suhas , Rode Chandrashekhar 
Published: September 2017

AbstractAn efficient one‐pot catalytic cascade sequence has been developed for the production of value‐added ethers from bioderived aldehydes. Etherification of 5‐(hydroxymethyl)furfural with different aliphatic alcohols over acidic Zr–montmorillonite (Zr‐Mont) catalyst produced a mixture of 5‐(alkoxymethyl)furfural and 2‐(dialkoxymethyl)‐5‐(alkoxymethyl)furan. The latter was selectively converted back into 5‐(alkoxymethyl)furfural by treating it with water over the same catalyst. The synthesis of 2,5‐bis(alkoxymethyl)furan was achieved through a cascade sequence involving etherification, transfer hydrogenation, and re‐etherification over a combination of acidic Zr‐Mont and the charge‐transfer hydrogenation catalyst [ZrO(OH)2]. This catalyst combination was further explored for the cascade conversion of 2‐furfuraldehyde into 2‐(alkoxymethyl)furan. The scope of this strategy was then extended for the reductive etherification of lignin‐derived arylaldehydes to obtain the respective benzyl ethers in >80 % yield. Additionally, the mixture of Zr‐Mont and ZrO(OH)2 does not undergo mutual destruction, which was proved by recycling experiments and XRD analysis. Both the catalysts were thoroughly characterized using BET, temperature‐programmed desorption of NH3 and CO2, pyridine‐FTIR, XRD, inductively coupled plasma optical emission spectroscopy, and X‐ray photoelectron spectroscopy techniques.
Biocatalytic Valorization of Furans: Opportunities for Inherently Unstable Substrates
Authors: Domínguez de María Pablo , Guajardo Nadia 
Published: September 2017

AbstractBiogenic furans (furfural and 5‐hydroxymethylfurfural) are expected to become relevant building blocks based on their high degree of functionality and versatility. However, the inherent instability of furans poses considerable challenges for their synthetic modifications. Valorization routes of furans typically generate byproducts, impurities, wastes, and a cumbersome downstream processing, compromising their ecological footprint. Biocatalysis may become an alternative, given the high selectivity of enzymes, together with the mild reaction conditions applied. This Review critically discusses the options for enzymes in the upgrading of furans. Based on previous reports, a variety of biocatalytic transformations have been applied to furans, with successful cases both in aqueous and in water‐free media. Options comprise the biodetoxification of toxic furans in hydrolysates, selective syntheses based on oxidation–reduction processes, solvent‐free esterifications, or carboligations to afford C12 derivatives. Reported strategies show in general promising but still modest productivities (2–30 gproduct L−1 d−1, depending on the example). There are opportunities with high potential and deserving of further development, scale‐up, and technoeconomic assessment, to entirely validate them as realistic alternatives.
Ultra‐Low Doses of Naltrexone Enhance the Antiallodynic Effect of Pregabalin or Gabapentin in Neuropathic Rats
Authors: Pineda‐Farias Jorge B. , Caram‐Salas Nadia L. , Salinas‐Abarca Ana B. , Ocampo Jorge , Granados‐Soto Vinicio 
Published: September 2017

ABSTRACT

Preclinical Research

Treatment of neuropathic pain is an area of largely unmet medical need. Pregabalin and gabapentin are anticonvulsants widely used for the treatment of neuropathic pain. Unfortunately, these drugs are only effective in 50–60% of the treated patients. In addition, both drugs have substantial side effects. Several studies have reported that ultralow doses of opioid receptor antagonists can induce analgesia and enhance the analgesic effect of opioids in rodents and humans. The objective of the present study was to assess the antiallodynic synergistic interaction between gabapentinoids and naltrexone in rats. Oral administration of pregabalin (ED50 = 2.79 ± 0.16 mg/kg) or gabapentin (ED50 = 21.04 ± 2.87 mg/kg) as well as intrathecal naltrexone (ED50 = 0.11 ± 0.02 ng) reduced in a dose‐dependent manner tactile allodynia in rats. Maximal antiallodynic effects (∼100%) were reached with 30 mg/kg of pregabalin, 300 mg/kg of gabapentin or 0.5 ng of naltrexone. Co‐administration of pregabalin or gabapentin and naltrexone in a fixed‐dose ratio (1:1) remarkably reduced spinal nerve ligation‐induced tactile allodynia showing a synergistic interaction. The data indicate that combinations of pregabalin or gabapentin and ultra‐low doses of naltrexone are able to reduce tactile allodynia in neuropathic rats with lower doses that those used when drugs are given individually and with an improved side effects profile. Drug Dev Res 78 : 371‐380, 2017. © 2017 Wiley Periodicals, Inc.
Disentangling shallow‐water bulk carbonate carbon isotope archives with evidence for multi‐stage diagenesis: An in‐depth component‐specific petrographic and geochemical study from Oman (mid‐Cretaceous)
Authors: Huck Stefan , Wohlwend Stephan , Coimbra Rute , Christ Nicolas , Weissert Helmut 
Published: September 2017

AbstractDisentangling shallow‐water bulk carbonate carbon isotope archives into primary and diagenetic components is a notoriously difficult task and even diagenetically screened records often provide chemostratigraphic patterns that significantly differ from global signals. This is mainly caused by the polygenetic nature of shallow‐water carbonate substrates, local carbon cycle processes causing considerable neritic–pelagic isotope gradients and the presence of hiatal surfaces resulting in extremely low carbonate preservation rates. Provided here is an in‐depth petrographic and geochemical evaluation of different carbonate phases of a mid‐Cretaceous (Barremian–Aptian) shallow‐water limestone succession (Jabal Madar section) deposited on the tropical Arabian carbonate platform in Oman. The superposition of stable isotope signatures of identified carbonate phases causes a complex and often noisy bulk carbon isotope pattern. Blocky sparite cements filling intergranular pores and bioclastic voids evidence intermediate to (arguably) deep burial diagenetic conditions during their formation, owing to different timing or differential faulting promoting the circulation of fluids from variable sources. In contrast, sparite cements filling sub‐vertical veins reveal a rock‐buffered diagenetic fluid composition with an intriguing moderate enrichment in 13C, probably due to fractionation during pressure release in the context of the Miocene exhumation of the carbonate platform under study. The presence of abundant, replacive dedolomite in mud‐supported limestone samples forced negative carbon and oxygen isotope changes that are either associated with the thermal breakdown of organic matter in the deep burial realm or the expulsion of buried meteoric water in the intermediate burial realm. Notwithstanding the documented stratigraphically variable and often facies‐related impact of different diagenetic fluids on the bulk‐rock stable isotope signature, the identification of diagenetic end‐members defined δ13C and δ18O threshold values that allowed the most reliable ‘primary’ bulk carbon isotope signatures to be extracted. Most importantly, this approach exemplifies how to place regional shallow‐water stable isotope patterns with evidence for a complex multi‐stage diagenetic history into a supraregional or even global context.
Rangifer management controls a climate‐sensitive tundra state transition
Authors: Bråthen Kari Anne , Ravolainen Virve Tuulia , Stien Audun , Tveraa Torkild , Ims Rolf A. 
Published: September 2017

AbstractRangifer (caribou/reindeer) management has been suggested to mitigate the temperature‐driven transition of Arctic tundra into a shrubland state, yet how this happens is uncertain. Here we study this much focused ecosystem state transition in riparian areas, where palatable willows (Salix) are dominant tall shrubs and highly responsive to climate change. For the state transition to take place, small life stages must become tall and abundant. Therefore we predicted that the performance of small life stages (potential recruits) of the tall shrubs were instrumental to the focal transition, where Rangifer managed at high population density would keep the small‐stage shrubs in a “browse trap” independent of summer temperature. We used a large‐scale quasi‐experimental study design that included real management units that spanned a wide range of Rangifer population densities and summer temperatures in order to assess the relative importance of these two driving variables. Ground surveys provided data on density and height of the small shrub life stages, while the distributional limit (shrubline) of established shrublands (the tall shrub life stage) was derived from aerial photographs. Where Rangifer densities were above a threshold of approximately 5 animals/km2, we found, in accordance with the expectation of a “browse trap,” that the small life stages of shrubs in grasslands were at low height and low abundance. At Rangifer densities below this threshold, the small life stages of shrubs were taller and more abundant indicating Rangifer were no longer in control of the grassland state. For the established shrubland state, we found that the shrubline was at a 100‐m lower elevation in the management units where Rangifer had been browsing in summer as opposed to the migratory ranges with no browsing in summer. In both seasonal ranges, the shrubline increased 100 m per 1°C increment in temperature. Our study supports the proposal that Rangifer management within a sustainable range of animal densities can mitigate the much‐focused transition from grassland to shrubland in a warming Arctic.
Ecological niche comparison and molecular phylogeny segregate the invasive moss species Campylopus introflexus (Leucobryaceae, Bryophyta) from its closest relatives
Authors: Gama Renato , Aguirre‐Gutiérrez Jesús , Stech Michael 
Published: September 2017

AbstractThe delimitation of the invasive moss species Campylopus introflexus from its closest relative, Campylopus pilifer, has been long debated based on morphology. Previous molecular phylogenetic reconstructions based on the nuclear ribosomal internal transcribed spacers (ITS) 1 and 2 showed that C. pilifer is split into an Old World and a New World lineage, but remained partly inconclusive concerning the relationships between these two clades and C. introflexus. Analyses of an extended ITS dataset displayed statistically supported incongruence between ITS1 and ITS2. ITS1 separates the New World clade of C. pilifer from a clade comprising C. introflexus and the Old World C. pilifer. Ancestral state reconstruction showed that this topology is morphologically supported by differences in the height of the dorsal costal lamellae in leaf cross‐section (despite some overlap). ITS2, in contrast, supports the current morphological species concept, i.e., separating C. introflexus from C. pilifer, which is morphologically supported by the orientation of the hyaline hair point at leaf apex as well as costal lamellae height. Re‐analysis of published and newly generated plastid atpB‐rbcL spacer sequences supported the three ITS lineages. Ecological niche modeling proved a useful approach and showed that all three molecular lineages occupy distinct environmental spaces that are similar, but undoubtedly not equivalent. In line with the ITS1 topology, the C. pilifer lineage from the New World occupies the most distinct environmental niche, whereas the niches of Old World C. pilifer and C. introflexus are very similar. Taking the inferences from ecological niche comparisons, phylogenetics, and morphology together, we conclude that all three molecular lineages represent different taxa that should be recognized as independent species, viz. C. introflexus, C. pilifer (Old World clade), and the reinstated C. lamellatus Mont. (New World clade).
Woody structure facilitates invasion of woody plants by providing perches for birds
Authors: Prather Chelse M. , Huynh Andrew , Pennings Steven C. 
Published: September 2017

AbstractWoody encroachment threatens prairie ecosystems globally, and thus understanding the mechanisms that facilitate woody encroachment is of critical importance. Coastal tallgrass prairies along the Gulf Coast of the US are currently threatened by the spread of several species of woody plants. We studied a coastal tallgrass prairie in Texas, USA, to determine if existing woody structure increased the supply of seeds from woody plants via dispersal by birds. Specifically, we determined if (i) more seedlings of an invasive tree (Tridacia sebifera) are present surrounding a native woody plant (Myrica cerifera); (ii) wooden perches increase the quantity of seeds dispersed to a grassland; and (iii) perches alter the composition of the seed rain seasonally in prairie habitats with differing amounts of native and invasive woody vegetation, both underneath and away from artificial wooden perches. More T. sebifera seedlings were found within M. cerifera patches than in graminoid‐dominated areas. Although perches did not affect the total number of seeds, perches changed the composition of seed rain to be less dominated by grasses and forbs. Specifically, 20–30 times as many seeds of two invasive species of woody plants were found underneath perches independent of background vegetation, especially during months when seed rain was highest. These results suggest that existing woody structure in a grassland can promote further woody encroachment by enhancing seed dispersal by birds. This finding argues for management to reduce woody plant abundance before exotic plants set seeds and argues against the use of artificial perches as a restoration technique in grasslands threatened by woody species.
Seasonal dynamics in mosquito abundance and temperature do not influence avian malaria prevalence in the Himalayan foothills
Authors: Ishtiaq Farah , Bowden Christopher G. R. , Jhala Yadvendradev V. 
Published: September 2017

AbstractWe examined seasonal prevalence in avian haemosporidians (PlasmodiumandHaemoproteus) in migrant and resident birds in western Himalaya, India. We investigated how infection with haemosporidians in avian hosts is associated with temporal changes in temperature and mosquito abundance along with host abundance and life‐history traits (body mass). Using molecular methods for parasite detection and sequencing partial cytochromebgene, 12Plasmodiumand 27Haemoproteuslineages were isolated. Our 1‐year study from December 2008 to December 2009 in tropical Himalayan foothills revealed a lack of seasonal variation inPlasmodiumspp. prevalence in birds despite a strong correlation between mosquito abundance and temperature. The probability of infection withPlasmodiumdecreased with increase in temperature. Total parasite prevalence and specificallyPlasmodiumprevalence showed an increase with average avian body mass. In addition, total prevalence exhibited a U‐shaped relationship with avian host abundance. There was no difference in prevalence ofPlasmodiumspp. orHaemoproteusspp. across altitudes; parasite prevalence in high‐altitude locations was mainly driven by the seasonal migrants. OneHaemoproteuslineage showed cross‐species infections between migrant and resident birds. This is the first molecular study in the tropical Himalayan bird community that emphasizes the importance of studying seasonal variation in parasite prevalence. Our study provides a basis for further evolutionary study on the epidemiology of avian malaria and spread of disease across Himalayan bird communities, which may not have been exposed to vectors and parasites throughout the year, with consequential implications to the risk of infection to naïve resident birds in high altitude.