bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solar forcing of Nile discharge and sapropel S1 formation in the early to middle Holocene eastern Mediterranean
Authors: Hennekam Rick , Jilbert Tom , Schnetger Bernhard , de Lange Gert J. 
Published: April 2014

AbstractWe present high‐resolution records for oxygen isotopes of the planktic foraminifer Globigerinoides ruber (δ18Oruber) and bulk sediment inorganic geochemistry for Holocene‐age sediments from the southeast Mediterranean. Our δ18Oruber record appears to be dominated by Nile discharge rather than basin‐scale salinity/temperature changes. Nile discharge was enhanced in the early to middle Holocene relative to today. The timing of the long‐term maximum in Nile discharge during the early Holocene corresponds to the timing of maximum intensity of the Indian Ocean‐influenced Southwest Indian summer monsoon (SIM). This coincidence suggests a major influence of an Indian Ocean moisture source on Nile discharge in the early to middle Holocene, while, presently, the Atlantic Ocean is the main moisture source. Nile discharge was highly variable on multicentennial time scale during the early to middle Holocene, being strongly influenced by variable solar activity. This solar‐driven variability is also recorded in contemporaneous SIM records, however, not observed in an Atlantic Ocean‐derived West African summer monsoon record from the Holocene. This supports the hypothesis that the Indian Ocean moisture source predominantly controlled Nile discharge at that time. Solar‐driven variability in Nile discharge also influenced paleoenvironmental conditions in the eastern Mediterranean. Bulk sediment Ba/Al and V/Al, used as indicators for (export) productivity and redox conditions, respectively, varied both in response to solar forcing on multicentennial time scales. We suggest that changes in Nile discharge on these time scales have been concordant with nutrient inputs to, and shallow ventilation of, the eastern Mediterranean.
Effect of soil properties on peat erosion and suspended sediment delivery in drained peatlands
Authors: Tuukkanen Tapio , Marttila Hannu , Kløve Bjørn 
Published: April 2014

AbstractErosion from peat extraction areas is known to cause siltation of water courses and poor water quality. However, the main soil parameters affecting peat erosion and suspended sediment (SS) yields from different catchments are not well understood. This paper used peat properties (degree of humification, peat type, ash content, porosity, moisture content, bulk density, and shear strength) and novel erosion threshold measurements from intact soil cores to explain peat erodibility and spatial variations in SS concentrations (SSCs) and SS loads (SSLs) at 20 Finnish peat extraction sites. The erosion threshold measurements suggested that critical shear stresses for particle entrainment decrease with increasing degree of humification (von Post scale) and are significantly lower in well‐decomposed peat than in slightly or moderately decomposed peat. Two critical shear stresses were obtained from moderately decomposed peat samples, indicating a degree of surface armoring by coarse peat fibers. Monitored long‐term average SSC was highest at study sites with well‐decomposed peat, while very fine‐grained mineral subsoil explained some of the highest long‐term SSC in areas where drainage ditches penetrated below the upper peat layer. Average SSL (kg d−1) at the study sites was best explained (R2 = 0.89) by average discharge and surface peat decomposition level. Overall, this study provides new knowledge on peat erosion and critical shear stresses that can be used in water conservation and sediment management practices for cutover peatlands and other similar land uses.
Chemoselective Synthesis of Unsymmetrical Internal Alkynes or Vinyl Sulfones via Palladium‐Catalyzed Cross‐Coupling Reaction of Sodium Sulfinates with Alkynes
Authors: Xu Yanli , Zhao Jinwu , Tang Xiaodong , Wu Wanqing , Jiang Huanfeng 
Published: April 2014

AbstractA highly efficient and mild palladium‐catalyzed cross‐coupling of sodium sulfinates and alkynes for the selective synthesis of unsymmetrical internal alkynes and vinyl sulfones has been developed. This methodology has advantages of easily accessible starting materials, functional group tolerance and a wide range of substrates, which provides rapid access to alkynes and vinyl sulfones.magnified image
Chemoselective Additions of Chloromethyllithium Carbenoid to Cyclic Enones: A Direct Access to Chloromethyl Allylic Alcohols
Authors: Pace Vittorio , Castoldi Laura , Holzer Wolfgang 
Published: April 2014

AbstractChloromethyllithium carbenoid has been chemoselectively added to cyclic enones (5‐, 6‐ and 7‐membered systems, including two natural products) to provide chloromethyl allylic alcohols. Under the optimized reaction conditions neither concomitant (n+1) homologation nor conjugate addition or Simmons–Smith‐like cyclopropanation takes place. The presence of LiBr is estimated to play a dual role, namely as a carbenoid stabilizer and mild Lewis acid activator of the CO group. Notably, the mesomeric effect caused by β‐heteroatom‐containing substituents promotes the attack of the reagent at the most activated position.magnified image
Titanium‐Catalyzed, One‐Pot Synthesis of 2‐Amino‐3‐cyano‐ pyridines
Authors: Dissanayake Amila A. , Staples Richard J. , Odom Aaron L. 
Published: April 2014

AbstractEarth‐abundant and inexpensive titanium can catalyze alkyne iminoamination, which generates tautomers of 1,3‐diimines. Upon treatment with base (DBU) and malononitrile, the multicomponent coupling product is converted to 2‐amino‐3‐cyanopyridines in a one‐pot procedure in good to modest yields. There is substantial control of regioselectivity for the substituents on the pyridine ring and on the 2‐amino group. Several studies were done that provide significant evidence for a Dimroth rearrangement mechanism for 2‐aminopyridine formation, including isolation of a 2‐imino‐1,2‐dihydropyridine intermediate that undergoes rearrangement under the reaction conditions.magnified image
Ruthenium‐ and Rhodium‐Catalyzed Dehydrogenative ortho‐Alkenylation of Benzylamines via Free Amino Group Directed CH Bond Cleavage
Authors: Suzuki Chiharu , Morimoto Keisuke , Hirano Koji , Satoh Tetsuya , Miura Masahiro 
Published: April 2014

AbstractThe dehydrogenative direct coupling of α,α‐disubstituted benzylamines with acrylates takes place efficiently at room temperature under ruthenium catalysis, accompanied by free amino group‐directed ortho‐alkenylation and successive cyclization to produce (isoindol‐1‐yl)acetic acid derivatives. The reactions using styrenes in place of acrylates proceed effectively in the presence of a rhodium catalyst rather than ruthenium.magnified image
A Novel Type of Luciferin from the Siberian Luminous Earthworm Fridericia heliota: Structure Elucidation by Spectral Studies and Total Synthesis
Authors: Petushkov Valentin N. , Dubinnyi Maxim A. , Tsarkova Aleksandra S. , Rodionova Natalja S. , Baranov Mikhail S. , Kublitski Vadim S. , Shimomura Osamu , Yampolsky Ilia V. 
Published: April 2014

AbstractThe structure elucidation and synthesis of the luciferin from the recently discovered luminous earthworm Fridericia heliota is reported. This luciferin is a key component of a novel ATP‐dependent bioluminescence system. UV, fluorescence, NMR, and HRMS spectroscopy studies were performed on 0.005 mg of the isolated substance and revealed four isomeric structures that conform to spectral data. These isomers were chemically synthesized and one of them was found to produce light when reacted with a protein extract from F. heliota. The novel luciferin was found to have an unusual extensively modified peptidic nature, thus implying an unprecedented mechanism of action.
Fluorescent Mimetics of CMP‐Neu5Ac Are Highly Potent, Cell‐Permeable Polarization Probes of Eukaryotic and Bacterial Sialyltransferases and Inhibit Cellular Sialylation
Authors: Preidl Johannes J. , Gnanapragassam Vinayaga S. , Lisurek Michael , Saupe Jörn , Horstkorte Rüdiger , Rademann Jörg 
Published: April 2014

AbstractOligosaccharides of the glycolipids and glycoproteins at the outer membranes of human cells carry terminal neuraminic acids, which are responsible for recognition events and adhesion of cells, bacteria, and virus particles. The synthesis of neuraminic acid containing glycosides is accomplished by intracellular sialyl transferases. Therefore, the chemical manipulation of cellular sialylation could be very important to interfere with cancer development, inflammations, and infections. The development and applications of the first nanomolar fluorescent inhibitors of sialyl transferases are described herein. The obtained carbohydrate‐nucleotide mimetics were found to bind all four commercially available and tested eukaryotic and bacterial sialyl transferases in a fluorescence polarization assay. Moreover, it was observed that the anionic mimetics intruded rapidly and efficiently into cells in vesicles and translocated to cellular organelles surrounding the nucleus of CHO cells. The new compounds inhibit cellular sialylation in two cell lines and open new perspectives for investigations of cellular sialylation.
A Base‐Free Neutral Phase‐Transfer Reaction System
Authors: Shirakawa Seiji , Wang Lijia , He Rongjun , Arimitsu Satoru , Maruoka Keiji 
Published: April 2014

AbstractAlthough phase‐transfer reactions catalyzed by using quaternary ammonium salts are generally believed to require base additives, we discovered that, even without any base additives, conjugate additions of 3‐substituted oxindoles to nitroolefins proceeded smoothly in the presence of lipophilic quaternary ammonium bromide under water–organic biphasic conditions. The mechanism of this novel base‐free neutral phase‐transfer reaction system is investigated and the assumed catalytic cycle is presented together with interesting effects of water and lipophilicity of the phase‐transfer catalyst. The base‐free neutral phase‐transfer reaction system can be applied to highly enantioselective conjugate addition and aldol reactions under the influence of chiral bifunctional ammonium bromides as key catalysts. The structure of the chiral ammonium enolate intermediate is discussed based on the single‐crystal X‐ray structures of relevant ammonium salts and the importance of bifunctional design of catalyst is clearly explained in the model of intermediate.
Paläoklimaforschung auf dem Dach der Welt
Authors: Frenzel Peter , Günther Franziska , Kasper Thomas , Henkel Karoline 
Published: April 2014

AbstractBasierend auf mehreren Expeditionen geben wir einen kurzen Überblick über Methoden zur Rekonstruktion des Paläoklimas im Hochland von Tibet. Schwierige Arbeitsbedingungen in eingeschränkt zugänglichen und wenig erschlossenen Gebieten auf Höhen um 4500 m über dem Meeresspiegel sind für diese Expeditionen charakteristisch. Neben sedimentologischen und geochemischen Analysen sind es vor allem Mikrofossilien und Biomarker, die als Archive von Umweltveränderungen der jüngeren geologischen Vergangenheit genutzt werden, da sie gut verfügbar und vielseitig interpretierbar sind. Veränderungen des Seespiegels, der Wasserchemie, von biologischer Produktivität, Temperatur, Vegetation und anderen Parametern sind mit diesen Methoden rekonstruierbar. Ihre prozessorientierte Interpretation ermöglicht es, räumliche und zeitliche Verschiebungen des Monsunsystems zu identifizieren.
MOOCs – Lernen im Internet
Authors: Buldun Can , Illenberger Susanne , Springer Sebastian 
Published: April 2014

AbstractMassive open online courses (oder “MOOCs”) sind kostenlose, internetbasierte Kurse, in denen Sachverhalte anschaulich und kurzweilig dargestellt werden. Die Zahl der angebotenen Kurse steigt rasant und das Spektrum an Themengebieten ist nahezu unbegrenzt.??Unser englischsprachiger MOOC “DNA – from structure to therapy” wendet sich an Schüler von Gymnasien und High Schools auf der ganzen Welt, die an Biologie interessiert sind und womöglich eine Karriere in den Lebenswissenschaften planen. Obwohl das Konzept von MOOCs derzeit noch nicht vollständig ausgereift ist, haben MOOCs aufgrund ihrer zahlreichen Vorteile ein hohes Potenzial, ein fester Bestandteil der weltweiten Bildungslandschaft zu werden.
Dicke Brummer: Schein‐Hummeln und das Insekt des Jahres
Authors: Petrischak Hannes 
Published: April 2014

AbstractFliegen haben in weiten Teilen der Bevölkerung nicht gerade den besten Ruf, gelten sie doch bei wenig differenzierter Betrachtung als lästig oder sogar eklig. Doch sie wecken durch Mimikry, als nützliche Räuber, spezialisierte Parasitoide oder begehrte Beutetiere anderer Insekten schnell das Interesse des aufmerksamen Natur‐Beobachters. Eine Wanzenfliege hat es nun sogar zum “Insekt des Jahres” geschafft.
Determination of pinocembrin in human plasma by solid‐phase extraction and LC/MS/MS: application to pharmacokinetic studies
Authors: Yan Bei , Cao Guoying , Sun Taohua , Zhao Xi , Hu Xin , Yan Jiling , Peng Yueying , Shi Aixin , Li Yang , Xue Wei , Li Min , Li Kexin , Liu Yingfa 
Published: April 2014

ABSTRACTA sensitive, fast and specific method for the quantitation of pinocembrin in human plasma based on high‐performance liquid chromatography–tandem mass spectrometry (LC/MS/MS) was developed and validated. Clonazepam was used as the internal standard (IS). After solid‐phase extraction of 500 μL plasma, pinocembrin and the IS were separated on a Luna C8 column using the mobile phase composed of acetonitrile–0.3 mm ammonium acetate solution (65:35, v/v) at a flow rate of 0.25 mL/min in isocratic mode. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring via an electrospray ionization source in negative mode by AB SCIEX Qtrap 5500. The assay was linear from 1 to 400 ng/mL, with within‐ and between‐run accuracy (relative error) from −1.82 to 0.54%, and within‐ and between‐run precision (CV) below 5.25%. The recovery was above 88% for the analyte at 1, 50 and 300 ng/mL. This analytical method was successful for the determination of pinocembrin in human plasma and applied to a pharmacokinetic study of pinocembrin injection in healthy volunteers after intravenous drip administration. Copyright © 2014 John Wiley & Sons, Ltd.
Analysis of parabens in dentifrices and the oral cavity
Authors: Park Yong‐Duk , Jang Jong‐Hwa , Park Jung‐Eun , Kim Ji Hyun , Kim Eun‐Cheol , Song Yun‐Jung , Kwon Ha‐Jeong 
Published: April 2014

ABSTRACTThis study analyzed levels of parabens in commercial dentifrices and saliva. HPLC was performed using 35% acetonitrile and measuring absorbance at 254 nm. Thirteen toothpastes and five mouthwashes were analyzed. Of these, volunteers used three toothpastes and two mouthwashes, and levels of parabens were analyzed in saliva and water used for mouth rinsing. In toothpastes, the highest concentrations of methylparaben (MP), propylparaben (PP) and n‐butylparaben (nBP) were 1.86, 1.42 and 1.87 mg/g, respectively. In mouthwashes, the highest concentrations of MP and PP were 0.97 and 0.11 mg/mL, respectively. After volunteers used 500 mg toothpaste T‐1, which contained 895 µg MP, the first and tenth mouth rinse samples contained means of 64.63 and 1.89 µg MP, respectively. After rinsing the mouth three or five times, 37 µg or 18 µg MP was calculated to remain in the oral cavity, respectively. After using 20 mL mouthwash S‐1, which contained 19 mg MP, 1.53 mg MP was calculated to remain in the oral cavity. Immediately after using this mouthwash, the mean salivary concentration of MP was 237 µg/mL. The daily intake of parabens from dentifrices was predicted to be insignificant compared with the intake from food; however, parabens can be ingested from dentifrices. Copyright © 2014 John Wiley & Sons, Ltd.
Structural Basis of Furan–Amino Acid Recognition by a Polyspecific Aminoacyl‐tRNA‐Synthetase and its Genetic Encoding in Human Cells
Authors: Schmidt Moritz J. , Weber Annemarie , Pott Moritz , Welte Wolfram , Summerer Daniel 
Published: April 2014

AbstractThe site‐selective introduction of photo‐crosslinking groups into proteins enables the discovery and mapping of weak and/or transient protein interactions with high spatiotemporal resolution, both in vitro and in vivo. We report the genetic encoding of a furan‐based, photo‐crosslinking amino acid in human cells; it can be activated with red light, thus offering high penetration depths in biological samples. This is achieved by activation of the amino acid and charging to its cognate tRNA by a pyrrolysyl‐tRNA‐synthetase (PylRS) mutant with broad polyspecificity. To gain insights into the recognition of this amino acid and to provide a rationale for its polyspecificity, we solved three crystal structures of the PylRS mutant: in its apo‐form, in complex with adenosine 5′‐(β,γ‐imido)triphosphate (AMP‐PNP) and in complex with the AMP ester of the furan amino acid. These structures provide clues for the observed polyspecificity and represent a promising starting point for the engineering of PylRS mutants with further increased substrate scope.
Synthesis and Peroxidase‐Like Activity of Salt‐Resistant Platinum Nanoparticles by Using Bovine Serum Albumin as the Scaffold
Authors: He Shao‐Bin , Deng Hao‐Hua , Liu Ai‐Lin , Li Guang‐Wen , Lin Xin‐Hua , Chen Wei , Xia Xing‐Hua 
Published: April 2014

AbstractA green approach is proposed for the synthesis of Pt nanoparticles (PtNPs) in the bovine serum albumin (BSA) scaffold through biomineralization. The resulting BSA–PtNPs have been proved to function as peroxidase mimics that can catalyze the reaction of various peroxidase substrates in the presence of H2O2. Kinetic studies indicate that BSA–PtNPs have a much higher affinity for H2O2 than the NPs of other Pt‐based peroxidase mimics. Furthermore, the BSA shell plays an important role in promoting the robust stability of PtNPs. Even in high ionic strength environment (2 M NaCl), the catalytic activity can be well preserved. These excellent properties make the BSA–PtNPs an ideal candidate for a wide range of potential applications as peroxidase mimics.
Assembly of a Nanoreactor System with Confined Magnetite Core and Shell for Enhanced Fenton‐Like Catalysis
Authors: Zeng Tao , Zhang Xiaole , Wang Saihua , Ma Yurong , Niu Hongyun , Cai Yaqi 
Published: April 2014

AbstractConventional solid catalysts for heterogeneous Fenton‐like reactions in bulk solution usually suffer from aggregation and vulnerability, which greatly lower the catalytic efficiency and hamper their practical application. Herein, we demonstrate a promising yolk–shell nanostructure with both the core and the shell composed of magnetite (designated as yolk‐like Fe3O4@Fe3O4/C) as a nanoreactor capable of accommodating the Fenton‐like reaction into its void space. Benefiting from the mesoporous shell and perfect interior cavity of this composite, reactants can access and be abundantly confined within the microenvironment where Fe3O4 sites are dispersed on the entire cavity surfaces, thus leading to a higher catalytic efficiency compared with the conventional solid catalysts in bulk solution. The chosen model reaction of chlorophenols degradation in the presence of the as‐prepared materials as well as hydrogen peroxide (H2O2) confirms this assumption. Under the optimal reaction conditions, more than 97 % 4‐chlorophenol (4‐CP) can be degraded in the Fe3O4@Fe3O4/C nanoreactor, whereas only 28 % can be achieved by using bare Fe3O4 particles within 60 min. Furthermore, owing to the existence of the outermost carbon layer and high‐magnetization properties, the nanoreactor can be re‐used for several runs. The synthesized nanoreactor displays superior catalytic activity toward the Fenton‐like reaction compared with the bare solid catalysts, and thereby holds significant potential for practical application in environmental remediation.
Azacyanines of the Pyrrolopyrrole Series
Authors: Marks Timo , Daltrozzo Ewald , Zumbusch Andreas 
Published: April 2014

AbstractThe reaction of POCl3‐activated, readily soluble diketopyrrolopyrrole (DPP) with 2‐aminoheteroaromatics to yield 1:1 and 1:2 hydrogen chelates is described. Complexation of these hydrogen chelates with boron reagents results in thermally and photochemically stable fluorescent dyes (PP–azacyanines). The 1:2 complexes in particular absorb at long wavelengths and are brightly fluorescing. The rich photophysics of the new compounds are presented. Both the pronounced vibrational fine structure of the S0→S1 transitions and the observed fluorescence phenomena allow detailed conclusions to be made on the correlation between molecular structure and optical properties.
A Compact Tetrathiafulvalene–Benzothiadiazole Dyad and Its Highly Symmetrical Charge‐Transfer Salt: Ordered Donor π‐Stacks Closely Bound to Their Acceptors
Authors: Geng Yan , Pfattner Raphael , Campos Antonio , Hauser Jürg , Laukhin Vladimir , Puigdollers Joaquim , Veciana Jaume , Mas‐Torrent Marta , Rovira Concepció , Decurtins Silvio , Liu Shi‐Xia 
Published: April 2014

AbstractA compact and planar donor–acceptor molecule 1 comprising tetrathiafulvalene (TTF) and benzothiadiazole (BTD) units has been synthesised and experimentally characterised by structural, optical, and electrochemical methods. Solution‐processed and thermally evaporated thin films of 1 have also been explored as active materials in organic field‐effect transistors (OFETs). For these devices, hole field‐effect mobilities of μFE=(1.3±0.5)×10−3 and (2.7±0.4)×10−3 cm2 V s−1 were determined for the solution‐processed and thermally evaporated thin films, respectively. An intense intramolecular charge‐transfer (ICT) transition at around 495 nm dominates the optical absorption spectrum of the neutral dyad, which also shows a weak emission from its ICT state. The iodine‐induced oxidation of 1 leads to a partially oxidised crystalline charge‐transfer (CT) salt {(1)2I3}, and eventually also to a fully oxidised compound {1I3}⋅1/2I2. Single crystals of the former CT compound, exhibiting a highly symmetrical crystal structure, reveal a fairly good room temperature electrical conductivity of the order of 2 S cm−1. The one‐dimensional spin system bears compactly bonded BTD acceptors (spatial localisation of the LUMO) along its ridge.
Two‐Dimensional Assembly Based on Flow Supramolecular Chemistry: Kinetic Control of Molecular Interactions Under Solvent Diffusion
Authors: Numata Munenori , Kozawa Tomohiro 
Published: April 2014

AbstractSelf‐assembly of porphyrin molecules can be controlled kinetically to form structures with lengths extending from the nano‐ to the micrometer scale, through a programmed solvent‐diffusion process in designed microflow spaces. Temporal solvent structures generated in the microflow were successfully transcribed into molecular architectures.
Manganese(IV)‐Mediated Hydroperoxyarylation of Alkenes with Aryl Hydrazines and Dioxygen from Air
Authors: Kindt Stephanie , Jasch Hannelore , Heinrich Markus R. 
Published: April 2014

AbstractWe report a new carbooxygenation‐type version of the Meerwein arylation in which the introduction of oxygen is achieved by using dioxygen from the air. In this way, hydroperoxides were obtained from activated as well as non‐activated alkenes by oxidizing aryl hydrazines with manganese dioxide. The best results were obtained with α‐substituted acrylates. Importantly, the aryl hydrazine has to be added slowly to the reaction mixture to allow sufficient uptake of dioxygen from the air. Competition and labeling experiments revealed hydroperoxyl radicals as novel oxygen‐centered radical scavengers.