bluuebunny/crossref_metadata_2025_split huggingface dataset:
Divergence in floral trait preferences between nonflower‐specialized birds and insects on the Galápagos
Authors: Hervías‐Parejo Sandra , Heleno Ruben , Nogales Manuel , Olesen Jens M. , Traveset Anna 
Published: April 2019

Premise of the StudyThe characteristic scarcity of insects on remote oceanic islands has driven nonflower‐specialized vertebrates to broaden their trophic niches and explore floral resources. From our previous studies in the Galápagos, we know that native insectivorous and frugivorous birds visit a wide range of entomophilous flowers and can also act as effective pollinators. Here, we tested whether opportunistic Galápagos birds show any preference for specific floral traits, and if so, this preference differs from that of insects.MethodsSixteen floral morphology and nectar traits of 26 native species were studied, as well as the frequency with which they are visited by birds and insects. Nonmetric multidimensional scaling (NMDS) was used to evaluate the distribution of flower traits values along two main dimensions and measure the similarity between the plants visited mostly by birds versus those by insects.Key ResultsNMDS of floral traits resulted in two species groups: (1) bell‐shaped, white flowers with wider corollas at nectary level and higher nectar volume, associated with high bird visitation rates; and (2) bowl and tubular‐shaped flowers with narrower corollas at nectary level and lower nectar volume, associated with high insect visitation rates.ConclusionsDespite the divergence in floral trait preferences between opportunistic Galápagos birds and insects, bird‐visited flowers display mixed traits not fitting the classical ornithophilous syndrome. This finding is compatible with the existence of a transitional or bet‐hedging phenotype between insect and bird visitors and underscores the importance of coevolution and floral diversification in nonspecialized plant–visitor interactions.
Developing Through‐Space Charge Transfer Polymers as a General Approach to Realize Full‐Color and White Emission with Thermally Activated Delayed Fluorescence
Authors: Hu Jun , Li Qiang , Wang Xingdong , Shao Shiyang , Wang Lixiang , Jing Xiabin , Wang Fosong 
Published: April 2019

AbstractThrough‐space charge transfer polymers (TSCT polymers) that contain a non‐conjugated polystyrene backbone and spatially separated donor and acceptor units for solution‐processed OLEDs with full‐color and white emission is reported. By tuning the charge transfer strength between donor and acceptors with different electron‐accepting ability, emission color spanning from deep blue to red can be achieved. By incorporating two kinds of donor/acceptor pairs in one polymer to create duplex through‐space charge‐transfer channels, blue and yellow emission can be simultaneously obtained to realize white electroluminescence from a single polymer. The TSCT polymers exhibit thermally activated delayed fluorescence effect with delayed‐component lifetimes in range of 0.36–1.98 μs, and unexpected aggregation‐induced emission (emission intensity enhancement of up to 117 from solution to aggregation state).
Access to a Key Building Block for the Prostaglandin Family via Stereocontrolled Organocatalytic Baeyer–Villiger Oxidation
Authors: Zhu Kejie , Hu Sha , Liu Minjie , Peng Haihui , Chen Fen‐Er 
Published: April 2019

AbstractA new protocol for the construction of a crucial bicyclic lactone of prostaglandins using a stereocontrolled organocatalytic Baeyer–Villiger (B‐V) oxidation was developed. The key B‐V oxidation of a racemic cyclobutanone derivative with aqueous hydrogen peroxide has enabled an early‐stage construction of a bicyclic lactone skeleton in high enantiomeric excess (up to 95 %). The generated bicyclic lactone is fully primed with two desired stereocenters and enabled the synthesis of the entire family of prostaglandins according to Corey′s route. Furthermore, the reactivity and enantioselectivity of B‐V oxidation of racemic bicyclic cyclobutanones were evaluated and 90–99 % ee was obtained, representing one of the most efficient routes to chiral lactones. This study further facilitates the synthesis of prostaglandins and chiral lactone‐containing natural products to promote drug discovery.
Mechanochromism, Twisted/Folded Structure Determination, and Derivatization of (N‐Phenylfluorenylidene)acridane
Authors: Matsuo Yutaka , Wang Ya , Ueno Hiroshi , Nakagawa Takafumi , Okada Hiroshi 
Published: April 2019

Abstract(N‐Phenylfluorenylidene)acridane (Ph‐FA) compounds with electron‐withdrawing and ‐donating substituents (H, MeO, Ph, NO2, Br, F) at the para position of the phenyl group were successfully synthesized by Barton–Kellogg reactions of N‐aryl thioacridones and diazofluorene. By using the substituent on the nitrogen atom to alter the electronic properties, both the folded and twisted conformers of p‐NO2‐C6H4‐FA could be crystallographically characterized, which enabled the charge transfer from the electron‐donating acridane moiety to the electron‐accepting fluorenylidene moiety to be understood. Ground‐state mechanochromism, thermochromism, vapochromism, and proton‐induced chromism were demonstrated between the folded and twisted conformations of the conformers. Protonation and chemical oxidation of Ph‐FA gave two stable acridinium compounds, namely, the fluorenylacridinium and acridinium radical cations. The present study will contribute to the development of functional dyes and organic semiconductors.
Heterodiatomare Mehrfachbindung zwischen Elementen der Gruppe 13: Ein Komplex mit B‐Al‐π‐Bindung reduziert CO2
Authors: Hofmann Alexander , Légaré Marc‐André , Wüst Leonie , Braunschweig Holger 
Published: April 2019

AbstractVerbindungen mit heterodiatomarer Mehrfachbindung zwischen Gruppe‐13‐Elementen sind bislang unbekannt. In dieser Zuschrift berichten wir über eine Darstellungsmethode von [(CAAC)PhB=AlCp3t] (1), einem Komplex, bei dem zwei Singulettfragmente nach Assoziation eine π‐Bindung zwischen Bor und Aluminium bilden. Neben den Eigenschaften dieser Mehrfachbindung wird die Reaktivität von 1 gegenüber CO2 präsentiert. Diese führt über eine ungewöhnliche Metathesereaktion zu einer B‐CO‐Verbindung.
Sr6Cd2Sb6O7S10: Strong SHG Response Activated by Highly Polarizable Sb/O/S Groups
Authors: Wang Ruiqi , Liang Fei , Wang Fakun , Guo Yangwu , Zhang Xian , Xiao Yi , Bu Kejun , Lin Zheshuai , Yao Jiyong , Zhai Tianyou , Huang Fuqiang 
Published: April 2019

AbstractA new nonlinear optical (NLO) oxysulfide, Sr6Cd2Sb6O7S10, which contains the functional groups [SbOxS5−x]7− (x=0, 1) with a 5s2 electron configuration, is synthesized by a solid‐state reaction. This compound displays a phase‐matchable second harmonic generation (SHG) response four times stronger than AgGaS2 (AGS) under laser irradiation at 2.09 μm. Single‐crystal‐based optical measurements reveal a SHG intensity that can be tuned by temperature and novel photoluminescence properties. Theoretical analyses demonstrate that tetragonal [SbOS4]7− and [SbS5]7− pyramids make the predominant contribution to the enhanced SHG effect. Among those, the [SbOS4]7− units with mixed anions make a larger contribution. This work proposes that oxysulfide groups with an ns2 electron configuration can serve as new functional building units in NLO materials and opens a new avenue for the design of other optoelectronic materials.
Cobalt‐Catalyzed Enantioselective Hydroboration/Cyclization of 1,7‐Enynes: Asymmetric Synthesis of Chiral Quinolinones Containing Quaternary Stereogenic Centers
Authors: Wu Caizhi , Liao Jiayu , Ge Shaozhong 
Published: April 2019

AbstractAn asymmetric cobalt‐catalyzed hydroboration/cyclization of 1,7‐enynes to synthesize chiral six‐membered N‐heterocyclic compounds was developed. A variety of aniline‐tethered 1,7‐enynes react with pinacolborane to afford the corresponding chiral boryl‐functionalized quinoline derivatives in high yields with high enantioselectivity. This cobalt‐catalyzed asymmetric cyclization of 1,7‐enyens provides a general approach to access a series of chiral quinoline derivatives containing quaternary stereocenters.
A Gas‐Phase CanMn4−nO4+ Cluster Model for the Oxygen‐Evolving Complex of Photosystem II
Authors: Mauthe Silvia , Fleischer Irene , Bernhardt Thorsten M. , Lang Sandra M. , Barnett Robert N. , Landman Uzi 
Published: April 2019

AbstractOne of the fundamental processes in nature, the oxidation of water, is catalyzed by a small CaMn3O4⋅MnO cluster located in photosystem II (PS II). Now, the first successful preparation of a series of isolated ligand‐free tetrameric CanMn4−nO4+ (n=0–4) cluster ions is reported, which are employed as structural models for the catalytically active site of PS II. Gas‐phase reactivity experiments with D2O and H218O in an ion trap reveal the facile deprotonation of multiple water molecules via hydroxylation of the cluster oxo bridges for all investigated clusters. However, only the mono‐calcium cluster CaMn3O4+ is observed to oxidize water via elimination of hydrogen peroxide. First‐principles density functional theory (DFT) calculations elucidate mechanistic details of the deprotonation and oxidation reactions mediated by CaMn3O4+ as well as the role of calcium.
Selenium‐Modified Microgels as Bio‐Inspired Oxidation Catalysts
Authors: Tan Kok H. , Xu Wenjing , Stefka Simon , Demco Dan E. , Kharandiuk Tetiana , Ivasiv Volodymyr , Nebesnyi Roman , Petrovskii Vladislav S. , Potemkin Igor I. , Pich Andrij 
Published: April 2019

AbstractActive colloidal catalysts inspired by glutathione peroxidase (GPx) were synthesized by integration of catalytically active selenium (Se) moieties into aqueous microgels. A diselenide crosslinker (Se X‐linker) was successfully synthesized and incorporated into microgels through precipitation polymerization, along with the conventional crosslinker N,N′‐methylenebis(acrylamide) (BIS). Diselenide bonds within the microgels were cleaved through oxidation by H2O2 and converted to seleninic acid whilst maintaining the intact microgel microstructure. Through this approach catalytically active microgels with variable amounts of seleninic acid were synthesized. Remarkably, the microgels exhibited higher catalytic activity and selectivity at low reaction temperatures than the molecular Se catalyst in a model oxidation reaction of acrolein to acrylic acid and methyl acrylate.
The Rise of Fiber Electronics
Authors: Xu Xiaojie , Xie Songlin , Zhang Ye , Peng Huisheng 
Published: April 2019

AbstractAs a new direction in applied chemistry, fiber electronics allow device configuration to evolve from three to two dimensions and then to one dimension. The reduction in dimension brings unique properties, such as ultraflexibility, tissue adaptability, and weavability, enabling their use in a variety of applications, particularly in various emerging fields related to implantable devices and wearable systems. The different types of fiber electrode materials are summarized based on the one‐dimensional configuration and their distinctive interfaces, various devices, and promising applications. The remaining challenges and future directions are finally highlighted.
Biomimetic Chiral Photonic Crystals
Authors: Lv Jiawei , Ding Defang , Yang Xuekang , Hou Ke , Miao Xiang , Wang Dawei , Kou Baichuan , Huang Ling , Tang Zhiyong 
Published: April 2019

AbstractAlthough it is well known that the amazing iridescent colors of the cuticle of beetles reflect the intricate nanoscale organization of bio‐fibers, artificial inorganic materials with comparable optical responses have not yet been synthesized from abiotic nanoscale building blocks. Such materials could find broad applications, including in circular polarizers, to generate circularly polarized luminescence, or in lasers. Herein, we describe a general method for the fabrication of biomimetic chiral photonic crystals by Langmuir–Schaefer assembly of colloidal inorganic nanowires. We not only reproduced the intricate helical structure and circularly polarized color reflection observed in beetles, but also achieved the highest chiroptical activity with a dissymmetry factor of −1.6 ever reported for chiral inorganic nanostructures. More importantly, the programmable structural control based on the precise interlayer arrangement endows us with unprecedented freedom to manipulate the optical activity of as‐fabricated chiral photonic crystals.
Spectroscopic, textural, electrical and magnetic properties of antimicrobial nano Fe(III) Schiff base complex
Authors: Mousa Emad S. , Mahmoud Walaa H. 
Published: April 2019

A novel Schiff base ligand (L) was prepared through condensation of 2,6‐diaminopyridine and dibenzoyl methane in a 1:1 ratio. This Schiff base ligand was used for complex formation reaction with Fe(III) chloride. The structures of the ligand and its complex were deduced from elemental analyses, mass spectroscopy, 1H NMR, IR, UV‐Vis, electronic spectra, magnetic moment, molar conductivity measurements, thermogravimetric analyses and X‐ray diffraction. The molecular and electronic structures of both ligand and complex were optimized theoretically using density function theory (DFT) method. Moreover, the antimicrobial activities of the prepared compounds were studied and proven against some pathogenic bacteria. The Fe(III) complex had higher biological activity than that of the free ligand. Proceeding from the collected information, the properties of the complex were further investigated. The particle size was determined by dynamic light scattering technique to be 92.59 nm. Textural properties of the nano complex were studied by N2 adsorption to estimate the specific surface area, pore volume and pore size distribution. The pores in the complex were found in the micropore–mesopore range. Differential scanning calorimetric measurements reveal the existence of four endothermic peaks at 243.8, 308, 339.8 and 380.5 K. Dielectric properties and conductivity were scanned at different frequencies and temperatures. The dielectric constant reaches a peak value of 600 at ~390 K, 30 Hz. A cross‐over from the universal dielectric response to the super linear power law of conductivity was reported for this complex at T ≤ 345 K. Finally, the AC‐magnetic susceptibility measurements were carried out in the low‐temperature region. The complex showed paramagnetic behavior with a slight change in the magnitude of its magnetic moment at T = 244 K.
A transformation‐based approach to Gaussian mixture density estimation for bounded data
Authors: Scrucca Luca 
Published: April 2019

AbstractFinite mixture of Gaussian distributions provide a flexible semiparametric methodology for density estimation when the continuous variables under investigation have no boundaries. However, in practical applications, variables may be partially bounded (e.g., taking nonnegative values) or completely bounded (e.g., taking values in the unit interval). In this case, the standard Gaussian finite mixture model assigns nonzero densities to any possible values, even to those outside the ranges where the variables are defined, hence resulting in potentially severe bias. In this paper, we propose a transformation‐based approach for Gaussian mixture modeling in case of bounded variables. The basic idea is to carry out density estimation not on the original data but on appropriately transformed data. Then, the density for the original data can be obtained by a change of variables. Both the transformation parameters and the parameters of the Gaussian mixture are jointly estimated by the expectation‐maximization (EM) algorithm. The methodology for partially and completely bounded data is illustrated using both simulated data and real data applications.
Whole‐bacterium ribosome display selection for isolation of highly specific anti‐Staphyloccocus aureus Affitins for detection‐ and capture‐based biomedical applications
Authors: Béhar Ghislaine , Renodon‐Cornière Axelle , Kambarev Stanimir , Vukojicic Petar , Caroff Nathalie , Corvec Stéphane , Mouratou Barbara , Pecorari Frédéric 
Published: April 2019

AbstractDetection and capture methods using antibodies have been developed to ensure identification of pathogens in biological samples. Though antibodies have many attractive properties, they also have limitations and there are needs to expand the panel of available affinity proteins with different properties. Affitins, that we developed from the Sul7d proteins, are a solid class of affinity proteins, which can be used as substitutes to antibodies or to complement them. We report the generation and characterization of antibacterial Affitins with high specificity for Staphylococcus aureus. For the first time, ribosome display selections were carried out using whole‐living‐cell and naïve combinatorial libraries, which avoid production of protein targets and immunization of animals. We showed that Affitin C5 exclusively recognizes S. aureus among dozens of strains, including clinical ones. C5 binds staphylococcal Protein A (SpA) with a K
D of 108 ± 2 nM and has a high thermostability (T
m = 77.0°C). Anti‐S. aureus C5 binds SpA or bacteria in various detection and capture applications, including ELISA, western blot analysis, bead‐fishing, and fluorescence imaging. Thus, novel anti‐bacteria Affitins which are cost‐effective, stable, and small can be rapidly and fully designed in vitro with high affinity and specificity for a surface‐exposed marker. This class of reagents can be useful in diagnostic and biomedical applications.
New insights into the performance characteristics of the Planova‐series hollow‐fiber parvovirus filters using confocal and electron microscopy
Authors: Nazem‐Bokaee Hadi , Chen Dayue , O'Donnell Sean Michael , Zydney Andrew L. 
Published: April 2019

AbstractVirus filtration remains a critical step in the downstream process for the production of monoclonal antibodies and other mammalian cell‐derived biotherapeutics. Recent studies have shown large differences in virus capture behavior of different virus filters, although the origin of these differences is still unclear. The objective of this study was to use confocal and scanning electron microscopy to directly evaluate the capture of virus‐size nanoparticles in Planova 20N and BioEX hollow‐fiber virus filters. Confocal images of fluorescent nanoparticles were quantified using ImageJ image processing software based on the measured fluorescence intensity of the labeled nanoparticles. Nanoparticle capture by the Planova BioEX was independent of transmembrane pressure from 10 to 45 psi. In contrast, the Planova 20N showed significant differences in nanoparticle capture profile at low pressure, consistent with literature data showing virus breakthrough under these conditions. Images obtained after a process interruption show significant migration of previously captured nanoparticles in the Planova 20N filters but not in the BioEX. These results provide important insights into the nature of virus capture in different virus filters and its dependence on the underlying structure of the virus filtration membranes.
Structural and Energetic Impact of Non‐natural 7‐Deaza‐8‐azaguanine, 7‐Deaza‐8‐azaisoguanine, and Their 7‐Substituted Derivatives on Hydrogen‐Bond Pairing with Cytosine and Isocytosine
Authors: Chawla Mohit , Minenkov Yury , Vu Khanh B. , Oliva Romina , Cavallo Luigi 
Published: April 2019

AbstractThe impact of 7‐deaza‐8‐azaguanine (DAG) and 7‐deaza‐8‐azaisoguanine (DAiG) modifications on the geometry and stability of the G:C Watson–Crick (cWW) base pair and the G:iC and iG:C reverse Watson–Crick (tWW) base pairs has been characterized theoretically. In addition, the effect on the same base pairs of seven C7‐substituted DAG and DAiG derivatives, some of which have been previously experimentally characterized, has been investigated. Calculations indicate that all of these modifications have a negligible impact on the geometry of the above base pairs, and that modification of the heterocycle skeleton has a small impact on the base‐pair interaction energies. Instead, base‐pair interaction energies are dependent on the nature of the C7 substituent. For the 7‐substituted DAG‐C cWW systems, a linear correlation between the base‐pair interaction energy and the Hammett constant of the 7‐substituent is found, with higher interaction energies corresponding to more electron‐withdrawing substituents. Therefore, the explored modifications are expected to be accommodated in both parallel and antiparallel nucleic acid duplexes without perturbing their geometry, while the strength of a base pair (and duplex) featuring a DAG modification can, in principle, be tuned by incorporating different substituents at the C7 position.
Agar versus Agarose Gelled Electrolyte for In Situ Corrosion Studies on Metallic Cultural Heritage
Authors: Ramírez Barat Blanca , Cano Emilio 
Published: April 2019

AbstractThe use of gelled electrolytes has revealed an interesting solution for in situ electrochemical measures on cultural heritage, where liquid electrolytes cannot be easily handled. After developing an agar gelled electrolyte cell, other gelling agents such as agarose are being considered to improve it. In this work, the performance of agarose gels in different concentrations has been studied and compared to agar and a liquid electrolyte. Measurements have been done on patinated quaternary bronze and weathering steel, as representative materials of outdoor monuments. Agarose gels have been validated for in situ corrosion studies on bronze and weathering steel sculptures.
Synthesis of Off‐Stoichiometric CoS Nanoplates from a Molecular Precursor for Efficient H2/O2 Evolution and Supercapacitance
Authors: Gervas Charles , Khan Malik Dilshad , Mlowe Sixberth , Zhang Chunyang , Zhao Chen , Gupta Ram K. , Akerman Matthew P. , Mashazi Philani , Nyokong Tebello , Revaprasadu Neerish 
Published: April 2019

AbstractThe development of cost‐effective and easily accessible bifunctional materials, which can be effectively used for energy storage and energy generation, is highly desirable. Herein, a new molecular precursor [tris(morpholinodithiocarbamato)Co(III)] has been synthesized and the X‐ray crystal structure of the complex determined. The precursor was used to prepare oleylamine (OLA)‐capped cobalt sulfide nanoplatelets, using a facile hot injection method at two different temperatures (200 °C and 260 °C). The characterization of the samples shows that CoS synthesized at 200 °C is slightly sulfur rich, whereas CoS synthesized at 260 °C is slightly cobalt rich. The effect of off‐stoichiometry of CoS nanoplatelets on the energy generation and storage applications was studied. The oxygen evolution reaction catalytic performance of both samples indicate overpotentials of 307 and 276 mV as well as Tafel slopes of 96 and 82 mV/dec, respectively. Similarly, overpotentials of 132 and 153 mV were observed for the hydrogen evolution reaction, with Tafel slopes of 159 and 154 mV/dec, respectively. The capacitive behavior of the samples was also examined, and specific capacitance values of 298 and 440 F/g were obtained with cycling stabilities of 73 and 97 %, after 5000 cycles, respectively. The results indicate that sulfur‐deficient CoS can show superior performance for efficient energy generation and storage devices.