bluuebunny/crossref_metadata_2025_split huggingface dataset:
R CrB: Long‐period variations of radial velocity and velocity of outflow
Authors: Rosenbush A. 
Published: July 2019

The recently discovered variation in the mean radial velocity (RV) of R CrB on a time scale of about 10,000 days may be associated with a long‐term pulsation of a star with the amplitude of about 2.5 km s−1, which results in the known mass loss of the star at the rate of 10−6 times the mass of the Sun. It is also possible the connection with the 46‐year cycle in the sequence of the great R CrB declines. The absence of an obvious connection between the onset of R CrB decline and a certain phase of the 40‐day pulsation is suggested to relate to a long time delay between the processes in the noncoherently pulsating photosphere and in the zone of dust condensation. The search for the long‐term variability of the RV of R CrB from the data of the recently published large homogeneous database made it possible to identify two types of unique behavior of the RV in the JD 2451500–2454400 interval immediately before the unique Great decline in 2007. At first, the RV showed a superposition of known 40‐day pulsations of six pulsations with a period of 238 days, an average velocity of 25 km s−1 and amplitude of 3 km s−1. Near JD 2454600, this pulsation was abruptly replaced by the 792‐day cycle. The cycle has a radically different half, with an average velocity about of 24.5 km s−1. The first half can be termed abnormal because of the unique central 40‐day pulsation with a very high amplitude of about 14 km s−1. The second half of cycle is a superposition of the half‐wave normal‐like prolonged pulsation and pulsations with a period of about 42 days and an amplitude of about 3 km s−1. At the beginning of the third cycle, the IV Great RCB‐type decline started.
Multi‐spectroscopic and molecular dynamics simulations investigation of the binding mechanism of polybrominated diphenyl ethers to hen egg white lysozyme
Authors: Zuo Yanqiu , Rui Yuefan , Xu Jie , Yang Lulu , Yi Zhongsheng 
Published: July 2019

AbstractThree PBDEs (BDE25, BDE47, and BDE154) were selected to investigate the interactions between PBDEs and hen egg white lysozyme (HEWL) by molecular modeling, fluorescence spectroscopy, and FT‐IR spectra. The docking results showed that hydrogen bonds were formed between BDE25 and residue TRP63 and between BDE47 and TRP63 with bond lengths of 2.178 Å and 2.146 Å, respectively. The molecular dynamics simulations indicated that van der Waals forces played a predominant role in the binding of three PBDEs to HEWL. The observed fluorescence quenching can be attributed to the formation of complexes between HEWL and PBDEs, and the quenching mechanism is a static quenching. According to Förster's non‐radiative energy transfer theory, the binding distances r were < 7 nm, indicating a high probability of energy transfer from HEWL to the three PBDEs. The synchronous fluorescence showed that the emission maximum wavelength of tryptophan (TRP) residues emerged a red‐shift. FT‐IR spectra indicated that BDE25, BDE47 and BDE154 induced the α‐helix percentage of HEWL decreased from 32.70% ± 1.64% to 28.27% ± 1.41%, 27.50% ± 1.38% and 29.78% ± 1.49%, respectively, whereas the percentage of random coil increased from 26.67% ± 1.33% to 27.60% ± 1.38%, 29.18% ± 1.46% and 30.59% ± 1.53%, respectively.
Simultaneous determination of eight bioactive components of Cirsium setosum flavonoids in rat plasma using triple quadrupole LC/MS and its application to a pharmacokinetic study
Authors: Wang He Chen , Bao Yong Rui , Wang Shuai , Li Tian Jiao , Meng Xian Sheng 
Published: July 2019

AbstractCirsium setosum (Willd.) MB. has been reported to exert significant anti‐hemorrhagic, anti‐inflammation, antimicrobial, sedative and detoxicating efficacy. It has been widely used to treat gastrointestinal bleeding, uterine bleeding, infectious hepatitis and cardiovascular disease in China. Recent studies have shown that flavonoids are the main active components in C. setosum. Nevertheless, to the best of our knowledge, there is no report concerning the simultaneous determinations and pharmacokinetics of constituents in C. setosum flavonoids in rat plasma. In this study, a rapid, sensitive and selective triple quadrupole liquid chromatography–mass spectrometry method was developed to determine eight analytes from the flavonoids of C. setosum in rat plasma. In addition, the pharmacokinetic study of the eight analytes in rats after oral administration of C. setosum flavonoids was successfully completed through this method. According to the pharmacokinetic parameters of the eight analytes, rutin, naringin, quercetin, acacetin, wogonin were the long‐acting components of the C. setosum flavonoids, with long elimination time and high bioavailability. Of note, the method developed in this study fills a blank in pharmacokinetic studies of C. setosum flavonoids. Our findings provide valuable views on the understanding of the absorption mechanism of C. setosum flavonoids and their clinical efficacy.
Cuceolatins A–D: New Bioactive Diterpenoids from the Leaves of Cunninghamia lanceolata
Authors: Yu Jin‐Hai , Yu Zhi‐Pu , Wu Dong‐Xiang , Yan Xue , Wang Yin‐Yin , Zhang Hua 
Published: July 2019

AbstractFour new diterpenoids named cuceolatins A–D, including three labdane‐type (1–3) and one abietane‐type (4) as well as three known labdane analogs (5–7), were reported from the leaves of Cunninghamia lanceolata. Structural assignments for these compounds were conducted by analyses of spectroscopic data, and their absolute configurations were determined by time‐dependent density functional theory (TD‐DFT) based electronic circular dichroism (ECD) calculations. Among them, the abietane‐type diterpenoid (11‐hydroxy‐12‐methoxyabieta‐8,11,13‐trien‐3‐one (4)) showed significant cytotoxicity against human MDA‐MB‐231, MCF‐7, and HeLa tumor cell lines with IC50 measurements of 4.3, 2.8 and 4.5 μm, respectively, while the labdane‐type diterpenoids with a 4α‐carboxy group (1–3 and 5) exhibited moderate antibacterial activity towards Bacillus subtilis and Staphylococcus aureus with IC50 values all below 25 μm.
Noble Metal Supported on Activated Carbon for “Hydrogen Free” HDO Reactions: Exploring Economically Advantageous Routes for Biomass Valorisation
Authors: Jin Wei , Santos José Luis , Pastor‐Perez Laura , Gu Sai , Centeno Miguel Angel , Reina Tomas Ramirez 
Published: July 2019

AbstractAn innovative route for bio‐compounds upgrading via “hydrogen‐free” hydrodeoxygenation (HDO) is proposed and evaluated using guaiacol as a model compound in a high‐pressure batch reactor. Experimental results showed that noble metal supported on activated carbon catalysts are able to conduct tandem multiple steps including water splitting and subsequent HDO. The activity of Ru/C catalyst is superior to other studied catalysts (i. e. Au/C, Pd/C and Rh/C) in our water‐only HDO reaction system. The greater dispersion and smaller metal particle size confirmed by the TEM micrographs accounts for the better performance of Ru/C. This material also presents excellent levels of stability as demonstrated in multiple recyclability runs. Overall, the proposed novel approach confirmed the viability of oxygenated bio‐compounds upgrading in a water‐only reaction system suppressing the need of external H2 supply and can be rendered as a fundamental finding for the economical biomass valorisation to produce added value bio‐fuels.
High‐Spin and Low‐Spin Perferryl Intermediates in Fe(PDP)‐Catalyzed Epoxidations
Authors: Zima Alexandra M. , Lyakin Oleg Y. , Bryliakov Konstantin P. , Talsi Evgenii P. 
Published: July 2019

AbstractTwo bioinspired hydroxo‐bridged diferric complexes 6 and 7 with N4‐donor ligands of the PDP type (PDP=N,N′‐bis(pyridin‐2‐ylmethyl)‐2,2′‐bipyrrolidine), differing by substituents at the pyridine rings (4‐NMe2 in 7 vs. 3,5‐Me2‐4‐OMe in 6), efficiently catalyze the enantioselective alkene epoxidation with H2O2 and peracetic acid in the presence of a carboxylic acid additive (up to 99 catalyst turnover numbers, TON, toward epoxide, up to 94 % ee). Catalyst systems based on complex 7 display the high‐spin perferryl intermediate 7 aAA (S=3/2, g1, g2=3.69, g3=1.96), whereas catalyst systems based on complex 6 exhibit the low‐spin perferryl intermediate 6 aAA (S=1/2, g1=2.07, g2=2.01, g3=1.96). The S=3/2 and the S=1/2 intermediates directly react with cyclohexene and cyclohexane at low temperatures (−40 °C and −85 °C, respectively). The catalyst systems, exhibiting less reactive intermediate 7 aAA, demonstrate higher enantioselectivity (% ee) in the epoxidation of chalcone. The origin of the unprecedented high‐spin state of the perferryl intermediate is discussed.
Bioelectrocatalysis on Anodized Epitaxial Graphene and Conventional Graphitic Interfaces
Authors: Vagin Mikhail Yu. , Sekretaryova Alina N. , Håkansson Anna , Iakimov Tihomir , Ivanov Ivan G. , Syväjärvi Mikael , Yakimova Rositsa , Lundström Ingemar , Eriksson Mats 
Published: July 2019

AbstractGraphitic materials exhibit significant anisotropy due to the difference in conductivity in a single layer and between adjacent layers. This anisotropy is manifested on epitaxial graphene (EG), which can be manipulated on the nanoscale in order to provide tailor‐made properties. Insertion of defects into the EG lattice was utilized here for controllable surface modification with a model biocatalyst and the properties were quantified by both electrochemical and optical methods. A comparative evaluation of the electrode reaction kinetics on the enzyme‐modified 2D material vs conventional carbon electrode materials revealed a significant enhancement of mediated bioelectrocatalysis at the nanoscale.
Recent Advances in Zinc‐Containing Colloidal Semiconductor Nanocrystals for Optoelectronic and Energy Conversion Applications
Authors: Chen Dechao , Wang Aixiang , Buntine Mark A. , Jia Guohua 
Published: July 2019

AbstractColloidal semiconductor nanocrystals (NCs), especially cadmium (Cd)‐ and lead (Pb)‐containing ones, have been proved to be the promising materials for photoelectronic energy conversion applications. However, the high toxicity and cost of these materials restrict their widespread use. Zinc (Zn)‐containing colloidal semiconductor NCs are non‐/less toxic and environmentally friendly materials, manifesting in stimulating optical and electronic properties with relevance to a broad scope of applications including light‐emitting diodes (LEDs), sensors, photocatalysts, and more. In this Review, we elaborate on the shape control of Zn‐containing colloidal semiconductor NCs achieved by a variety of wet‐chemical synthetic approaches. Moreover, the formation of core‐shell, doped, and hybrid structures based on Zn‐containing colloidal semiconductor NCs allow for the optimization of their functionalities, which underpin stimulating photoelectronic energy conversion applications in quantum‐dot LEDs (QLEDs), photodetectors, and photocatalysis. Zn‐containing colloidal semiconductor NCs that combine the green chemistry with sustainable developments possess a bright future.
Impact of a Water‐Soluble Gallic Acid‐Based Dendrimer on the Color‐Stabilizing Mechanisms of Anthocyanins
Authors: Cruz Luís , Basílio Nuno , Mendoza Johan , Mateus Nuno , de Freitas Victor , Tawara Maun H. , Correa Juan , Fernandez‐Megia Eduardo 
Published: July 2019

AbstractThe interaction of two anthocyanins with a water‐soluble polyanionic dendrimer was studied through UV/Vis, stopped‐flow, and NMR spectroscopy. Cyanidin‐3‐glucoside (cy3glc) revealed a stronger interaction than malvidin‐3‐glucoside (mv3glc) at pH 1 according to their apparent association constants. A higher color increased was also obtained for cy3glc at pH 3.5 as a result of this stronger interaction. A high‐frequency chemical shift of the cy3glc aromatic protons suggest the formation of ionic pairs. The interaction parameters (K≈700 m−1, n≈295) indicated the binding of approximately two anthocyanin molecules by each sulfate group. The equilibrium and rate constants of cy3glc in the presence of dendrimer showed an increased stability of the flavylium cation and a higher protection of this species from hydration (pK′a and pKh increased almost one pH unit). The tuning and color stabilization of anthocyanins by using this dendrimer allow novel applications as colorimetric sensors for food packaging.
Beryllium‐Induced Conversion of Aldehydes
Authors: Müller Matthias , Buchner Magnus R. 
Published: July 2019

AbstractAldehydes play a key role in the human metabolism. Therefore, it is essential to know their reactivity with beryllium compounds in order to assess its effects in the body. The reactivity of simple aldehydes towards beryllium halides (F, Cl, Br, I) was studied through solution and solid‐state techniques and revealed distinctively different reactivities of the beryllium halides, with BeF2 being the least and BeI2 the most reactive. Rearrangement and aldol condensation reactions were observed and monitored by in situ NMR spectroscopy. Crystal structures of various compounds obtained by Be2+‐catalyzed cyclization, rearrangement, and aldol addition reactions or ligation of beryllium halides have been determined, including unprecedented one‐dimensional BeCl2 chains and the first structurally characterized example of an 1‐iodo‐alkoxide. Long‐term studies showed that only aldehydes without a β‐H can form stable beryllium complexes, whereas other aldehydes are oligo‐ and polymerized or decomposed by beryllium halides.
An Efficient Approach to Regio‐ and Stereodefined Fully‐Substituted Alkenylsilanes by Pd‐Catalyzed Allenic C(sp3)−H Oxidation
Authors: Zhu Can , Bäckvall Jan‐E. 
Published: July 2019

AbstractA highly efficient palladium‐catalyzed functionalization of allenylsilanes to give regio‐ and stereodefined fully‐substituted alkenylsilanes has been developed. This oxidative coupling reaction showed good functional group compatibility with exclusive regio‐ and stereoselectivity. The pending olefin on the silyl group was shown to be an indispensable element for the initial allenic C(sp3)−H bond cleavage, and performs as the directing group to control the overall selectivity. The addition of substoichiometric amounts of Et3N was found to increase the reaction rate leading to a higher reaction yield. The reaction can be easily scaled up and applied for the late‐stage functionalization of natural products and pharmaceutical compounds, including amino acids and steroid derivatives. The newly introduced functional groups include aryl, alkynyl, and boryl groups. The highly strained four‐membered ring, silacyclobutene was obtained when B2pin2 was employed as the coupling partner. Mechanistic studies, including kinetic isotope effects, showed that the allenic C(sp3)−H bond cleavage is the rate‐limiting step.
Copper‐Catalyzed Oxidative Dearomatization of 2‐Naphthols via Etherification
Authors: Yi Ji‐Cheng , Wu Zhi‐Jie , You Shu‐Li 
Published: July 2019

Summary of main observation and conclusionCopper‐catalyzed intermolecular oxidative‐etherification type dearomatization reaction of 2‐naphthols was developed. With air as the terminal oxidant, the reaction proceeded in excellent yields under mild conditions. In addition, the reaction between two different naphthol substrates occurred smoothly. A series of multifunctionalized β‐naphthalenones, important scaffold existed widely in natural products and biologically active molecules, were synthesized efficiently.
Synthesis of Substituted 5′‐Aminoadenosine Derivatives and Evaluation of Their Inhibitory Potential toward CD73
Authors: Ghoteimi Rayane , Nguyen >Van Tai , Rahimova Rahila , Grosjean Felix , Cros‐Perrial Emeline , Uttaro Jean‐Pierre , Mathé Christophe , Chaloin Laurent , Jordheim Lars Petter , Peyrottes Suzanne 
Published: July 2019

AbstractDerivatives of 5′‐aminoadenosine containing methyl carboxylate, methyl phosphonate, gem‐bisphosphonate, bis(methylphosphonate), and α‐carboxylmethylphosphonate or phosphonoacetate moieties were synthesized from key intermediate 5′‐aminonucleoside. These nucleotide analogues were envisaged as 5′‐mono‐ or diphosphate nucleoside mimics. All compounds were evaluated for CD73 inhibition in a cell‐based assay (MDA‐MB‐231) and toward the purified recombinant protein. Most of them failed to reach significant inhibition of AMP hydrolysis by CD73 at 100 μm. Among the new compounds, the most interesting candidates, 5 (5′‐deoxy‐5′‐N‐phosphonomethyladenosine) and 7 (5′‐deoxy‐5′‐N‐(ethoxyphosphorylacetate)adenosine), inhibited recombinant CD73 by 36 and 46 % and cellular CD73 by 61 and 45 % at 100 μm, respectively. Molecular modeling partially explains this lack of activity, as the initially predicted docking scores had been encouraging, especially for compound 9.
The Impact of Alkyl‐Chain Purity on Lipid‐Based Nucleic Acid Delivery Systems – Is the Utilization of Lipid Components with Technical Grade Justified?
Authors: Pawlowska Dorota , Janich Christopher , Langner Andreas , Dobner Bodo , Wölk Christian , Brezesinski Gerald 
Published: July 2019

AbstractThe physicochemical properties and transfection efficacies of two samples of a cationic lipid have been investigated and compared in 2D (monolayers at the air/liquid interface) and 3D (aqueous bulk dispersions) model systems using different techniques. The samples differ only in their chain composition due to the purity of the oleylamine (chain precursor). Lipid 8 (using the oleylamine of technical grade for cost‐efficient synthesis) shows lateral phase separation in the Langmuir layers. However, the amount of attached DNA, determined by IRRAS, is for both samples the same. In 3D systems, lipid 8 p forms cubic phases, which disappear after addition of DNA. At physiological temperatures, both lipids (alone and in mixture with cholesterol) assemble to lamellar aggregates and exhibit comparable DNA delivery efficiency. This study demonstrates that non‐lamellar structures are not compulsory for high transfection rates. The results legitimate the utilization of oleyl chains of technical grade in the synthesis of cationic transfection lipids.
Machine learning approach for secure communication in wireless video sensor networks against denial‐of‐service attacks
Authors: Ramesh Swaminathan , Yaashuwanth Calpakkam , Muthukrishnan Bala Anand 
Published: July 2019

SummaryMobile ad hoc networks (MANETs) own a flexible framework with the absence of a server, where conventional security components fail to compensate the level of MANET security conditions since it is confined to a particular environment, its data transfer potential, and battery and memory constrains. MANET provides a well‐grounded path and an efficiency in communication, but the confidentiality of the trust parameters remains a great challenge since it may be overheard by the impostor. This demands the need of exchanging the encrypted mathematical values. The proposed machine learning security paradigm provides firm and trustworthy network in spite of establishment over additional network platform. The QoS is improved through support vector machine for denial‐of‐service attack. The node has to be clustered to accomplish its respective task. The clustering is done with the help of LEACH protocol, where cluster head and Cluster member are fixed to transfer the data in the network. Low Energy adaptive clustering heirarchy (LEACH) propagates energy to abstain from draining of battery and malignant network. A secure framework is built along with encryption and decoding to protect from denial‐of‐service attack. Acknowledgement‐based flooding attack has been focused with the help of support vector machine algorithm. The messages are encoded in from the source node and coded again during transmission phase to obtain the original message. Defending the traditional methodologies, the proposed work provides excellent QoS when compared and tested with other protocols. The results obtained ensure its efficiency when support vector machine technique is combined with encryption scheme.
Genetic structure at three spatial scales is consistent with limited philopatry in Ricord's Rock Iguanas (Cyclura ricordii)
Authors: Carreras‐De León Rosanna , Pasachnik Stesha A. , Gerber Glenn P. , Brooks Christopher P. , Rupp Ernst , Welch Mark E. 
Published: July 2019

AbstractCyclura ricordiiis an endemic iguana from Hispaniola Island and is threatened on the IUCN Red List. The main threats are predation by introduced mammals, habitat destruction, and hunting pressure. The present study focused on two nesting sites from Pedernales Province in the Dominican Republic. The hypothesis that natal philopatry influences dispersal and nest‐site selection was tested. Monitoring and sampling took place in 2012 and 2013. Polymorphic markers were used to evaluate whether natal philopatry limits dispersal at multiple spatial scales. Ripley'sKrevealed that nests were significantly clustered at multiple scales, when both nesting sites were considered and within each nesting site. This suggests a patchy, nonrandom distribution of nests within nest sites. Hierarchical AMOVA revealed that nest‐site aggregations did not explain a significant portion of genetic variation within nesting sites. However, a small but positive correlation between geographic and genetic distance was detected using a Mantel's test. Hence, the relationship between geographic distance and genetic distance among hatchlings within nest sites, while detectable, was not strong enough to have a marked effect on fine‐scale genetic structure. Spatial and genetic data combined determined that the nesting sites included nesting females from multiple locations, and the hypothesis of “natal philopatry” was not supported because females nesting in the same cluster were no more closely related to each other than to other females from the same nesting site. These findings imply that nesting aggregations are more likely associated with cryptic habitat variables contributing to optimal nesting conditions.
Species‐level repertoire size predicts a correlation between individual song elaboration and reproductive success
Authors: Robinson Cristina M. , Creanza Nicole 
Published: July 2019

AbstractBirdsong has long been considered a sexually selected trait that relays honest information about male quality, and laboratory studies generally suggest that female songbirds prefer larger repertoires. However, analysis of field studies across species surprisingly revealed a weak correlation between song elaboration and reproductive success, and it remains unknown why only certain species show this correlation in nature. Taken together, these studies suggest that females in numerous species can detect and prefer larger repertoires in a laboratory setting, but larger individual repertoires correlate with reproductive success only in a subset of these species. This prompts the question: Do the species that show a stronger correlation between reproductive success and larger individual repertoires in nature have anything in common? In this study, we test whether between‐species differences in two song‐related variables—species average syllable repertoire size and adult song stability over time—can be used to predict the importance of individual song elaboration in reproductive success within a species. Our cross‐species meta‐analysis of field studies revealed that species with larger average syllable repertoire sizes exhibited a stronger correlation between individual elaboration and reproductive success than species with smaller syllable repertoires. Song stability versus plasticity in adulthood provided little predictive power on its own, suggesting that the putative correlation between repertoire size and age in open‐ended learners does not explain the association between song elaboration and reproductive success.