bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogenität der Luft/Wasser‐Grenzfläche gezeigt durch 2D‐HD‐SFE‐Spektroskopie
Authors: Hsieh Cho‐Shuen , Okuno Masanari , Hunger Johannes , Backus Ellen H. G. , Nagata Yuki , Bonn Mischa 
Published: June 2014

AbstractWassermoleküle wechselwirken stark miteinander durch Wasserstoffbrücken. Diese effiziente intermolekulare Kopplung verursacht eine starke Delokalisierung der Molekülschwingungen im Inneren des Wassers. Wir untersuchen die intermolekulare Kopplung der Schwingungen an der Luft/Wasser‐Grenzfläche und beobachten, dass die intermolekulare Kopplung 1) signifikant reduziert ist und 2) für verschiedene Wassermoleküle an der Grenzfläche stark variiert – während im Inneren des Wassers die Kopplung homogen ist. Für stark Wasserstoffbrücken‐gebundene O‐H‐Gruppen ist die Kopplung etwa zweimal geringer als im Inneren des Wassers, aufgrund der geringeren Dichte in der grenzflächennahen Region. Für schwach Wasserstoffbrücken‐gebundene O‐H‐Gruppen, die bei 3500 cm−1 absorbieren, ist diese Kopplung um einen weiteren Faktor ≈2 reduziert. Diese O‐H‐Gruppen werden den äußersten, jedoch Wasserstoffbrücken‐gebundenen Wassermolekülen zugeordnet, deren andere O‐H‐Gruppe zur Gasphase zeigt. Trotz der geringen strukturellen Einschränkungen durch die umgebenden Wasserstoffbrücken auf diese Wassermoleküle ist – bemerkenswerterweise – deren Strukturrelaxation langsam und die intermolekulare Kopplung schwach.
Two‐Coordinate Fe0 and Co0 Complexes Supported by Cyclic (alkyl)(amino)carbenes
Authors: Ung Gaël , Rittle Jonathan , Soleilhavoup Michele , Bertrand Guy , Peters Jonas C. 
Published: June 2014

AbstractThe CAAC [CAAC=cyclic (alkyl)(amino)carbene] family of carbene ligands have shown promise in stabilizing unusually low‐coordination number transition‐metal complexes in low formal oxidation states. Here we extend this narrative by demonstrating their utility in affording access to the first examples of two‐coordinate formal Fe0 and Co0 [(CAAC)2M] complexes, prepared by reduction of their corresponding two‐coordinate cationic FeI and CoI precursors. The stability of these species arises from the strong σ‐donating and π‐accepting properties of the supporting CAAC ligands, in addition to steric protection.
Redox and Anion Exchange Chemistry of a Stibine–Nickel Complex: Writing the L, X, Z Ligand Alphabet with a Single Element
Authors: Jones James S. , Wade Casey R. , Gabbaï François P. 
Published: June 2014

AbstractAccording to the covalent bond classification (CBC) method, two‐electron donors are defined as L‐type ligands, one‐electron donors as X‐type ligands, and two‐electron acceptors as Z‐type ligands. These three ligand functions are usually associated to the nature of the ligating atom, with phosphine, alkyl, and borane groups being prototypical examples of L‐, X‐ and Z‐ligands, respectively. A new SbNi platform is reported in which the ligating Sb atom can assume all three CBC ligand functions. Using both experimental and computational data, it is shown that PhICl2 oxidation of (o‐(Ph2P)C6H4)3SbNi(PPh3) (1) into [(o‐(Ph2P)C6H4)3ClSb]NiCl (2) is accompanied by a conversion of the stibine L‐type ligand of 1 into a stiboranyl X‐type ligand in 2. Furthermore, the reaction of 2 with the catecholate dianion in the presence of cyclohexyl isocyanide results in the formation of [(o‐(Ph2P)C6H4)3(o‐O2C6H4Sb)]Ni(CNCy) (4), a complex featuring a nickel atom coordinated by a Lewis acidic, Z‐type, stiborane ligand.
Ein‐, Zwei‐ und Drei‐Elektronen‐Reduktion eines CAAC‐SbCl3‐ Addukts
Authors: Kretschmer Robert , Ruiz David A. , Moore Curtis E. , Rheingold Arnold L. , Bertrand Guy 
Published: June 2014

AbstractDie Reaktion eines cyclischen Alkyl(amino)carbens mit SbCl3 führt zur Bildung des entsprechenden SbIII‐Addukts. Durch Ein‐Elektronen‐Reduktion kann daraus das erste Beispiel eines neutralen Antimon‐zentrierten Radikals in Lösung erhalten werden. Zwei‐Elektronen‐Reduktion führt zu einem Lewis‐Base‐stabilisierten Chlorstibiniden, und Drei‐Elektronen‐Reduktion ergibt schließlich eine diatomare Antimonspezies, die durch zwei Carbene stabilisiert ist. Das Radikal wurde mit EPR‐Spektroskopie charakterisiert, während die Strukturen der anderen drei Verbindungen durch Einkristall‐Röntgenbeugung bestimmt wurden. In diesen vier Spezies fällt die formale Oxidationsstufe des Metalloids von III auf II, auf I und schließlich auf 0.
Organocatalytic Asymmetric Hydrolysis of Epoxides
Authors: Monaco Mattia Riccardo , Prévost Sébastien , List Benjamin 
Published: June 2014

AbstractThe hydrolytic ring opening of epoxides is an important biosynthetic transformation and is also applied industrially. We report the first organocatalytic variant of this reaction, exploiting our recently discovered activation of carboxylic acids with chiral phosphoric acids via heterodimerization. The methodology mimics the enzymatic mechanism, which involves an enzyme‐bound carboxylate nucleophile. A newly designed phosphoric acid catalyst displays high stereocontrol in the desymmetrization of meso‐epoxides. The methodology shows wide generality with cyclic, acylic, aromatic, and aliphatic substrates. We also apply our method in the first highly enantioselective anti‐dihydroxylation of simple olefins.
Exploring Bis(cyclometalated) Ruthenium(II) Complexes as Active Catalyst Precursors: Room‐Temperature Alkene–Alkyne Coupling for 1,3‐Diene Synthesis
Authors: Zhang Jing , Ugrinov Angel , Zhang Yong , Zhao Pinjing 
Published: June 2014

AbstractDescribed is the development of a new class of bis(cyclometalated) ruthenium(II) catalyst precursors for CC coupling reactions between alkene and alkyne substrates. The complex [(cod)Ru(3‐methallyl)2] reacts with benzophenone imine or benzophenone in a 1:2 ratio to form bis(cyclometalated) ruthenium(II) complexes (1). The imine‐ligated complex 1 a promoted room‐temperature coupling between acrylic esters and amides with internal alkynes to form 1,3‐diene products. A proposed catalytic cycle involves CC bond formation by oxidative cyclization, β‐hydride elimination, and CH bond reductive elimination. This RuII/RuIV pathway is consistent with the observed catalytic reactivity of 1 a for mild tail‐to‐tail methyl acrylate dimerization and for cyclobutene formation by [2+2] norbornene/alkyne cycloaddition.
Aqueous Heterogeneity at the Air/Water Interface Revealed by 2D‐HD‐SFG Spectroscopy
Authors: Hsieh Cho‐Shuen , Okuno Masanari , Hunger Johannes , Backus Ellen H. G. , Nagata Yuki , Bonn Mischa 
Published: June 2014

AbstractWater molecules interact strongly with each other through hydrogen bonds. This efficient intermolecular coupling causes strong delocalization of molecular vibrations in bulk water. We study intermolecular coupling at the air/water interface and find intermolecular coupling 1) to be significantly reduced and 2) to vary strongly for different water molecules at the interface—whereas in bulk water the coupling is homogeneous. For strongly hydrogen‐bonded OH groups, coupling is roughly half of that of bulk water, due to the lower density in the near‐surface region. For weakly hydrogen‐bonded OH groups that absorb around 3500 cm−1, which are assigned to the outermost, yet hydrogen‐bonded OH groups pointing towards the liquid, coupling is further reduced by an additional factor of 2. Remarkably, despite the reduced structural constraints imposed by the interfacial hydrogen‐bond environment, the structural relaxation is slow and the intermolecular coupling of these water molecules is weak.
Continuous Flow Magnesiation of Functionalized Heterocycles and Acrylates with TMPMgCl⋅LiCl
Authors: Petersen Trine P. , Becker Matthias R. , Knochel Paul 
Published: June 2014

AbstractA flow procedure for the metalation of functionalized heterocycles (pyridines, pyrimidines, thiophenes, and thiazoles) and various acrylates using the strong, non‐nucleophilic base TMPMgCl⋅LiCl is reported. The flow conditions allow the magnesiations to be performed under more convenient conditions than the comparable batch reactions, which often require cryogenic temperatures and long reaction times. Moreover, the flow reactions are directly scalable without further optimization. Metalation under flow conditions also allows magnesiations that did not produce the desired products under batch conditions, such as the magnesiation of sensitive acrylic derivatives. The magnesiated species are subsequently quenched with various electrophiles, thereby introducing a broad range of functionalities.
NaOH modified P(acrylamide) hydrogel matrices for in situ metal nanoparticles preparation and their use in H2 generation from hydrolysis of NaBH4
Authors: Seven Fahriye , Sahiner Nurettin 
Published: June 2014

ABSTRACTCrosslinked poly(acrylamide) (p(AAm)) as neutral hydrogel is synthesized via photo polymerization technique, and the amide groups within p(AAm) matrices are converted to strongly ionizable carboxylic acids groups via facile modification route by simple treatment of NaOH to obtained NaOH‐p(AAm) hydrogels. Because of the highly ionizable nature of carboxylate groups within mod‐p(AAm), the swelling and metal ion absorbing capacities are increased tremendously, almost 40 and 7.5 folds, respectively. The Co(II) and Ni(II) metal ions are loaded into NaOH‐p(AAm) hydrogels, and are treated with NaBH4 to form corresponding metal nanoparticles in situ within mod‐p(AAm) matrices, and used in H2 generation production from hydrolysis of NaBH4. Various parameters such as functionality of polymeric matrices, the kinds and the amount of metal nanoparticles, and the temperature effecting the H2 generation are investigated. Comparable low Ea with the similar researches in the literature, Ea = 20.07 ± 0.05 kJ mol−1 is obtained in NaBH4 hydrolysis catalyzed by NaOH‐p(AAM)‐Co composite system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41106.
Abundance and movements of sperm whales in the western Mediterranean basin
Authors: Rendell L. , Simião S. , Brotons J. M. , Airoldi S. , Fasano D. , Gannier A. 
Published: June 2014

ABSTRACT

Sperm whales in the Mediterranean are classified as ‘Endangered’ by the IUCN. They are apparently isolated from adjacent Atlantic populations, and subject to anthropogenic pressures including interactions with illegal driftnet fisheries, ship strikes, ingestion of debris and underwater noise.
Photo‐identification data opportunistically collected from the western Mediterranean basin show that individual sperm whales regularly move in excess of 500 km across the western basin, suggesting that this area is occupied by a single population.
The best abundance estimate for this region is approximately 400 animals, with confidence intervals between 200 and 1000.
Given the mortality levels reported in the literature, this figure suggests that the conservation status of sperm whales in this region is very serious. Immediate priority should be placed both on conducting systematic surveys for abundance estimation and on measures to reduce the mortality associated with driftnet fishing. Copyright © 2014 John Wiley & Sons, Ltd.
Photo‐identification of sperm whales in the north‐western Mediterranean Sea: an assessment of natural markings
Authors: Alessi Jessica , Aïssi Mehdi , Fiori Cristina 
Published: June 2014

ABSTRACT

Photo‐identification is an important, non‐invasive tool that can be used to obtain data about cetacean population dynamics that are essential for proper environmental management. A standardized protocol is crucial for obtaining optimal results, particularly for long‐lived and highly migratory species such as sperm whales (Physeter macrocephalus) but also to study resident populations.
Photo‐identification of individuals using natural marks has been widely used to study sperm whales in the Mediterranean Sea. However, the prevalence of the marks used for identification is unknown. Thus, the goal of this study was to identify which mark types are most useful for identifying individual sperm whales.
A photo‐identification catalogue of sperm whales from the north‐western Mediterranean Sea was produced and examined to determine the most frequent mark types present on whales in the study area. Mark types and their distribution were described, prevalence and the size of each mark type were calculated, variability in visibility was investigated, and gain and loss rates were analysed.
Analysis of natural pigmentation may characterize sperm whale flanks in this study area as the best and most convenient element on which matching technique can be based. Indeed, this technique led to the identification of 97% of photographed individuals. Copyright © 2014 John Wiley & Sons, Ltd.
Ecotoxicological status of seven sperm whales (Physeter macrocephalus) stranded along the Adriatic coast of Southern Italy
Authors: Marsili Letizia , Maltese Silvia , Coppola Daniele , Carletti Laura , Mazzariol Sandro , Fossi M. Cristina 
Published: June 2014

ABSTRACT

In December 2009 seven male sperm whales (Physeter macrocephalus) stranded along the Adriatic coast of Southern Italy. Genetic and photo‐identification data indicated that these specimens belonged to the Mediterranean Sea population.
Complete necropsies were performed on the three best preserved animals. Blubber and muscle samples were collected from all seven specimens for contaminants analysis (DDTs, PCBs and PAHs) and biomarker responses (CYP1A1 and CYP2B) were evaluated from the three better preserved animals using western blot analysis.
Fibroblast cell cultures from two specimens were set up by culturing cell lines from integument tissue, to explore the susceptibility of these marine mammals to different xenobiotic compounds.
The levels of CYP1A1 and CYP2B, proteins that are induced by some POPs (DDTs and PCBs) and PAHs were detected using the indirect immunofluorescence assay. The results showed relatively high levels of contaminants, in particular from organochlorine xenobiotics, and strong responses of CYP1A1 and CYP2B reflecting toxicological stress of these sperm whales.
This is not considered to be their cause of death, but may have contributed to lowering the defences of their immune system. Copyright © 2014 John Wiley & Sons, Ltd.
Stereoselective Bromocyclization of Allylated Aldoxime Ethers
Authors: Egart Boris , Czekelius Constantin 
Published: June 2014

AbstractThe intramolecular bromoamination of allylated aldoxime ethers leads first to isoxazolidinium salts which then undergo a skeletal rearrangement to form bromo‐5,6‐dihydro‐4H‐1,3‐oxazines. Aliphatic aldoxime ethers with α‐protons undergo multiple brominations before rearrangement.
Sequence Elements Distal to the Ligand Binding Pocket Modulate the Efficiency of a Synthetic Riboswitch
Authors: Weigand Julia E. , Gottstein‐Schmidtke Sina R. , Demolli Shemsi , Groher Florian , Duchardt‐Ferner Elke , Wöhnert Jens , Suess Beatrix 
Published: June 2014

AbstractSynthetic riboswitches can serve as sophisticated genetic control devices in synthetic biology, regulating gene expression through direct RNA–ligand interactions. We analyzed a synthetic neomycin riboswitch, which folds into a stem loop structure with an internal loop important for ligand binding and regulation. It is closed by a terminal hexaloop containing a U‐turn and a looped‐out adenine. We investigated the relationship between sequence, structure, and biological activity in the terminal loop by saturating mutagenesis, ITC, and NMR. Mutants corresponding to the canonical U‐turn fold retained biological activity. An improvement of stacking interactions in the U‐turn led to an RNA element with slightly enhanced regulatory activity. For the first position of the U‐turn motif and the looped out base, sequence–activity relationships that could not initially be explained on the basis of the structure of the aptamer–ligand complex were observed. However, NMR studies of these mutants revealed subtle relationships between structure and dynamics of the aptamer in its free or bound state and biological activity.
Regio‐Selective Chemical‐Enzymatic Synthesis of Pyrimidine Nucleotides Facilitates RNA Structure and Dynamics Studies
Authors: Alvarado Luigi J. , LeBlanc Regan M. , Longhini Andrew P. , Keane Sarah C. , Jain Niyati , Yildiz Zehra F. , Tolbert Blanton S. , D'Souza Victoria M. , Summers Michael F. , Kreutz Christoph , Dayie T. Kwaku 
Published: June 2014

AbstractIsotope labeling has revolutionized NMR studies of small nucleic acids, but to extend this technology to larger RNAs, site‐specific labeling tools to expedite NMR structural and dynamics studies are required. Using enzymes from the pentose phosphate pathway, we coupled chemically synthesized uracil nucleobase with specifically 13C‐labeled ribose to synthesize both UTP and CTP in nearly quantitative yields. This chemoenzymatic method affords a cost‐effective preparation of labels that are unattainable by current methods. The methodology generates versatile 13C and 15N labeling patterns which, when employed with relaxation‐optimized NMR spectroscopy, effectively mitigate problems of rapid relaxation that result in low resolution and sensitivity. The methodology is demonstrated with RNAs of various sizes, complexity, and function: the exon splicing silencer 3 (27 nt), iron responsive element (29 nt), Pro‐tRNA (76 nt), and HIV‐1 core encapsidation signal (155 nt).
Mechanisms of hippocampal astrocytes mediation of spatial memory and theta rhythm by gliotransmitters and growth factors
Authors: Hassanpoor Hossein , Fallah Ali , Raza Mohsin 
Published: June 2014

AbstractOur knowledge about encoding and maintenance of spatial memory emphasizes the integrated functional role of the grid cells and the place cells of the hippocampus in the generation of theta rhythm in spatial memory formation. However, the role of astrocytes in these processes is often underestimated in their contribution to the required structural and functional characteristics of hippocampal neural network operative in spatial memory. We show that hippocampal astrocytes, by the secretion of gliotransmitters, such as glutamate, d‐serine, and ATP and growth factors such as BDNF and by the expression of receptors and channels such as those of TNFα and aquaporin, have several diverse fuctions in spatial memory. We specifically focus on the role of astrocytes on five phases of spatial memory: (1) theta rhythm generation, (2) theta phase precession, (3) formation of spatial memory by mapping data of entorhinal grid cells into the place cells, (4) storage of spatial information, and (5) maintenance of spatial memory. Finally, by reviewing the literature, we propose specific mechanisms mentioned in the form of a hypothesis suggesting that astrocytes are important in spatial memory formation.
The effect of hemin‐induced oxidative stress on erythropoietin production in HepG2 cells
Authors: Nishimura Kazuhiko , Tokida Masahiro , Katsuyama Hideaki , Nakagawa Hiroshi , Matsuo Saburo 
Published: June 2014

AbstractErythropoietin (EPO) and iron are both indispensable hematopoietic factors and are often studied in humans and rodents. Iron activates prolyl hydroxylases (PHDs) and promotes the degradation of the α‐subunit of hypoxia inducible factor (HIF), which regulates EPO production. Iron also causes oxidative stress. Oxidative stress leads to alterations in the levels of multiple factors that regulate HIF and EPO production. It is thought that iron influences EPO production by altering two pathways, namely PHDs activity and oxidative stress. We studied the differential effect of varying concentrations of hemin, an iron‐containing porphyrin, on EPO production in HepG2 cells. Hemin at 100 µM reduced EPO mRNA expression. The hemin‐induced reduction of EPO mRNA levels was attenuated at concentrations greater than 200 µM and EPO production increased in the presence of 500 µM hemin. In comparison, protoporphyrin IX, iron‐free hemin did not influence EPO mRNA expression. Additionally, malondialdehyde (MDA) concentrations and superoxide dismutase (SOD) activity significantly increased with 300 µM hemin. Importantly, the antioxidant tempol inhibited the hemin‐induced (500 µM) increase in EPO mRNA levels. In conclusion, these results suggest that restraint of EPO production by hemin was offset by the promotion of EPO production by hemin‐induced oxidative stress at hemin concentrations greater than 300 µM.
Catalytic Functionalization of Indoles by Copper‐Mediated Carbene Transfer
Authors: Delgado‐Rebollo Manuela , Prieto Auxiliadora , Pérez Pedro J. 
Published: June 2014

AbstractThe complex [TpBr3Cu(NCMe)] (TpBr3=hydrotris(3,4,5‐tribromo)pyrazolylborate) efficiently catalyzes the CH functionalization of indole derivatives at C3 by carbene transfer from different diazoesters in a high‐yield transformation involving low catalyst loadings and short reaction times. This system has shown that the previously proposed dichotomy of carbene addition (to the double bond) vs carbene insertion (to the CH bond) corresponds to two consecutive reaction steps: the cyclopropane intermediates, observed in the reaction mixtures, are the precursors of the final CH functionalization derivatives in a ring‐opening process involving acid catalysis. Those in situ generated cyclopropanes undergo nucleophilic ring opening with Me2CuLi to afford both C2 and C3 functionalized indoles.
Facile Synthesis of Porous PtM (M=Cu, Ni) Nanowires and Their Application as Efficient Electrocatalysts for Methanol Electrooxidation
Authors: Lai Jianping , Zhang Ling , Qi Wenjing , Zhao Jianming , Xu Min , Gao Wenyue , Xu Guobao 
Published: June 2014

AbstractPorous Pt75Cu25 and Pt73Ni27 nanowires were successfully synthesized by a one‐step wet chemical solution method without the use of any template for the first time. The combination of porous and one‐dimensional features and the addition of a second cheap metal offer high catalyst utilization, excellent catalytic activity, and better durability for the methanol oxidation reaction. Porous Pt75Cu25 and Pt73Ni27 nanowires showed mass current densities of 390 (at 0.69) and 503 mA mg−1 (at 0.70 V), respectively. These mass current densities are much higher than that of Pt nanowires (356 mA mg−1 at 0.73 V) and commercial Pt black (195 mA mg−1 at 0.73 V). During the entire 2000 s current–time test, the porous Pt75Cu25 and Pt73Ni27 nanowires also exhibited higher stability for the methanol oxidation reaction than Pt nanowires and commercial Pt black.
Enhanced Lithium‐Storage Performance from Three‐Dimensional MoS2 Nanosheets/Carbon Nanotube Paper
Authors: Li Hongsen , Wang Xiaoyan , Ding Bing , Pang Gang , Nie Ping , Shen Laifa , Zhang Xiaogang 
Published: June 2014

AbstractPromising energy‐storage behavior from molybdenum disulfide (MoS2) in the charging and discharging process is attributed to its layered, two‐dimensional structure, which enables convenient electrochemical reactions, but its performance is currently limited by inherent poor electrical conductivity. Herein, we report a facile and efficient method to fabricate a flexible, three‐dimensional, binder‐free electrode architecture consisting of highly conductive carbon nanotube paper conformally covered by MoS2 nanosheets. Its distinct advantages include abundant porous structure, highly conductive pathway for electrons, and fast transport channels for lithium ions. Electrochemical studies confirm that the MoS2 nanosheets/carbon nanotube paper electrode exhibits outstanding performance in terms of specific capacitance, rate capability, and cycling stability.