bluuebunny/crossref_metadata_2025_split huggingface dataset:
Double crests of peak height in the equatorial ionospheric F2 layer observed by COSMIC
Authors: Luan Xiaoli , Lei Jiuhou , Dou Xiankang , Dang Tong 
Published: December 2015

AbstractFor the first time, we report daytime double crests of peak height (hmF2) in the F2 layer based on the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) observations during 2007–2014. Evident double crests of hmF2 occurred at around ±10° geomagnetic latitude with a trough over the magnetic equator at low solar activity and at March equinox. This phenomenon is referred to as an equatorial height anomaly (EHA) of the ionospheric F2 layer. The double crests became less obvious at September equinox and disappeared at solstices. At solstices only one crest was observed in the summer hemisphere, which is probably associated with transequatorial neutral winds. In addition, the double EHA crests generally take place during 10:00–14:00 local times. Our results indicate that the EHA favors the conditions of strong vertical plasma drifts and weak transequatorial neutral winds during low solar activity. The EHA feature is reproduced by the Thermosphere Ionosphere Electrodynamics Global Circulation Model at March equinox and low solar activity.
Methane emissions from pan‐Arctic lakes during the 21st century: An analysis with process‐based models of lake evolution and biogeochemistry
Authors: Tan Zeli , Zhuang Qianlai 
Published: December 2015

AbstractThe importance of methane emissions from pan‐Arctic lakes in the global carbon cycle has been suggested by recent studies. These studies indicated that climate change influences this methane source mainly in two ways: the warming of lake sediments and the evolution of thermokarst lakes. Few studies have been conducted to quantify the two impacts together in a unified modeling framework. Here we adapt a region‐specific lake evolution model to the pan‐Arctic scale and couple it with a lake methane biogeochemical model to quantify the change of this freshwater methane source in the 21st century. Our simulations show that the extent of thaw lakes will increase throughout the 21st century in the northern lowlands of the pan‐Arctic where the reworking of epigenetic ice in drained lake basins will continue. The projected methane emissions by 2100 are 28.3 ± 4.5 Tg CH4 yr−1 under a low warming scenario (Representative Concentration Pathways (RCPs) 2.6) and 32.7 ± 5.2 Tg CH4 yr−1 under a high warming scenario (RCP 8.5), which are about 2.5 and 2.9 times the simulated present‐day emissions. Most of the emitted methane originates from nonpermafrost carbon stock. For permafrost carbon, the methanogenesis will mineralize a cumulative amount of 3.4 ± 0.8 Pg C under RCP 2.6 and 3.9 ± 0.9 Pg C under RCP 8.5 from 2006 to 2099. The projected emissions could increase atmospheric methane concentrations by 55.0–69.3 ppb. This study further indicates that the warming of lake sediments dominates the increase of methane emissions from pan‐Arctic lakes in the future.
Synthesis of Chiral Polyethers Containing Imidazolidinone Repeating Units and Application as Catalyst in Asymmetric Diels–Alder Reaction
Authors: Itsuno Shinichi , Oonami Tatsuaki , Takenaka Nagisa , Haraguchi Naoki 
Published: December 2015

AbstractIn this study, enantiopure imidazolidinones containing two hydroxyphenyl groups were synthesized, and the Williamson synthesis of the chiral bisphenols thus prepared with dihalides afforded polyethers containing chiral imidazolidinone repeating units. These chiral imidazolidinone polyethers exhibited excellent catalytic activity in the asymmetric Diels–Alder reaction. With the use of these polymeric catalysts, enantioselectivities up to 99% were obtained, higher than those obtained by the corresponding monomeric imidazolidinone catalyst in homogeneous solution. The polymeric catalysts were found to be insoluble in commonly used organic solvents, and they could be repeatedly used without the loss of activity.magnified image
Organocatalyzed Reduction of Tertiary Phosphine Oxides
Authors: Schirmer Marie‐Luis , Jopp Stefan , Holz Jens , Spannenberg Anke , Werner Thomas 
Published: December 2015

AbstractA novel selective catalytic reduction method of tertiary phosphine oxides to the corresponding phosphines has been developed. Notably, the reaction proceeds smoothly with low catalyst loadings of 1–5 mol% even at low temperature (70 °C). Under the optimized conditions various phosphine oxides could be selectively reduced and the desired phosphines were usually obtained in excellent yields above 90%. Furthermore, we have developed a one‐pot reaction sequence for the preparation of valuable phosphine⋅borane adducts. Simple addition of BH3⋅THF subsequent to the reduction step gave the desired adducts in yields up to 99%.magnified image
Synthesis of 4‐Aryl‐2‐Quinolones via Copper‐Catalyzed Hydroarylation of (o‐Aminophenyl)propiolates with Arylboronates
Authors: Murayama Tsukasa , Shibuya Masatoshi , Yamamoto Yoshihiko 
Published: December 2015

Abstract4‐Aryl‐2(1H)‐quinolones were efficiently synthesized via copper‐catalyzed hydroarylation of (o‐aminophenyl)propiolates with arylboronic acid neopentyl glycol esters. The substrate propiolates were prepared from the corresponding silylalkynes with carbon dioxide by Kondo’s carboxylation method using N,N‐dimethylformamide as a solvent. Hydroarylation was performed in the presence of 3 mol% copper(II) acetate in methanol at 28 °C for 12 h and subsequent deprotection using trifluoromethanesulfonic acid (3.0 equiv.) at 65 °C for 2 h in the same pot to afford the desired 4‐aryl‐2(1H)‐quinolones in 39–89% yields.magnified image
MORC2 mutations cause axonal Charcot–Marie–Tooth disease with pyramidal signs
Authors: Albulym Obaid M. , Kennerson Marina L. , Harms Matthew B. , Drew Alexander P. , Siddell Anna H. , Auer‐Grumbach Michaela , Pestronk Alan , Connolly Anne , Baloh Robert H. , Zuchner Stephan , Reddel Stephen W. , Nicholson Garth A. 
Published: December 2015

ObjectiveTo use linkage analysis and whole exome sequencing to identify the genetic mutation in a multigenerational Australian family with Charcot–Marie–Tooth disease type 2 (CMT2) and pyramidal signs.MethodsGenome‐wide linkage analysis was performed to map the locus. Whole exome sequencing was undertaken on selected individuals (3 affected, 1 normal), and segregation analysis and mutation screening were carried out using high‐resolution melt analysis. The GEM.app database was queried to identify additional families with mutations.ResultsSignificant linkage (2‐point LOD score ≥ +3) and haplotype analysis mapped a new locus for CMT2 and pyramidal signs to a 6.6Mb interval on chromosome 22q12.1–q12.3. Whole exome sequencing identified a novel mutation (p.R252W) in the microrchidia CW‐type zinc finger 2 (MORC2) gene mapping within the linkage region. The mutation fully segregated with the disease phenotype in the family. Screening additional families and querying unsolved CMT2 exomes, we identified the p.R252W mutation in 2 unrelated early onset CMT2 families and a second mutation p.E236G in 2 unrelated CMT2 families. Both the mutations occurred at highly conserved amino acid residues and were absent in the normal population.InterpretationWe have identified a new locus in which MORC2 mutations are the likely pathogenic cause of CMT2 and pyramidal signs in these families. MORC2 encodes the human CW‐type zinc finger 2 protein, which is a chromatin modifier involved in the regulation of DNA repair as well as gene transcription. ANN NEUROL 2016;79:419–427
Entropisch bedingte Selektivität der Kettenspaltung oder: Wo Makromoleküle sich trennen
Authors: Pahnke Kai , Brandt Josef , Gryn'ova Ganna , Lin Ching Y. , Altintas Ozcan , Schmidt Friedrich G. , Lederer Albena , Coote Michelle L. , Barner‐Kowollik Christopher 
Published: December 2015

AbstractWir zeigen, dass bei Beibehaltung aller anderen Bedingungen ein Bindungsbruch in der Mitte von Molekülen entropisch wesentlich bevorzugter abläuft als ein Bindungsbruch in endständiger Position. Vielfältige experimentelle wie theoretische Ansätze wurden genutzt, um die Selektivität des Bindungsbruchs oder der Dissoziation von in der Mitte oder am Ende des Moleküls kovalent oder supramolekular verbundener Addukte zu untersuchen. Die weitreichenden Auswirkungen auf andere Bereiche der Chemie, wie beispielsweise Kettentransferreaktionen, Polymerdegradation oder die Addition von Kontrollagenzien, werden diskutiert. Die beobachteten Effekte, welche auf entropische Faktoren zurückzuführen sind, wurden auf der Grundlage von einfachen theoretischen Modellen vorhergesagt und mittels Hochtemperatur(HT)‐NMR‐Spektroskopie von selbstorganisierten, supramolekularen Diblocksystemen sowie temperaturabhängiger Größenausschlusschromatographie (TD SEC) von kovalent verknüpften Diels‐Alder‐Stufenwachstumspolymeren überprüft.
A Strategy to Promote the Electrocatalytic Activity of Spinels for Oxygen Reduction by Structure Reversal
Authors: Wu Guangping , Wang Jun , Ding Wei , Nie Yao , Li Li , Qi Xueqiang , Chen Siguo , Wei Zidong 
Published: December 2015

AbstractThe electrocatalytic performance of a spinel for the oxygen reduction reaction (ORR) can be significantly promoted by reversing its crystalline structure from the normal to the inverse. As the spinel structure reversed, the activation and cleavage of O−O bonds are accelerated owing to a dissimilarity effect of the distinct metal atoms co‐occupying octahedral sites. The CoIIFeIIICoIIIO4 spinel with the Fe and Co co‐occupying inverse structure exhibits an excellent ORR activity, which even exceeds that of the state‐of‐the‐art commercial Pt/C by 42 mV in alkaline medium.
Solution‐State 17O Quadrupole Central‐Transition NMR Spectroscopy in the Active Site of Tryptophan Synthase
Authors: Young Robert P. , Caulkins Bethany G. , Borchardt Dan , Bulloch Daryl N. , Larive Cynthia K. , Dunn Michael F. , Mueller Leonard J. 
Published: December 2015

AbstractOxygen is an essential participant in the acid–base chemistry that takes place within many enzyme active sites, yet has remained virtually silent as a probe in NMR spectroscopy. Here, we demonstrate the first use of solution‐state 17O quadrupole central‐transition NMR spectroscopy to characterize enzymatic intermediates under conditions of active catalysis. In the 143 kDa pyridoxal‐5′‐phosphate‐dependent enzyme tryptophan synthase, reactions of the α‐aminoacrylate intermediate with the nucleophiles indoline and 2‐aminophenol correlate with an upfield shift of the substrate carboxylate oxygen resonances. First principles calculations suggest that the increased shieldings for these quinonoid intermediates result from the net increase in the charge density of the substrate–cofactor π‐bonding network, particularly at the adjacent α‐carbon site.
Eine skalierbare Synthese sequenzdefinierter Makromoleküle mit hohen Ausbeuten
Authors: Solleder Susanne C. , Zengel Deniz , Wetzel Katharina S. , Meier Michael A. R. 
Published: December 2015

AbstractHier wird ein effizienter Ansatz zur Synthese eines sequenzdefinierten Decamers, dessen Selbstmetathese sowie die Charakterisierung der erhaltenen Makromoleküle beschrieben. Zu diesem Zweck wurde ein monogeschütztes AB‐Monomer synthetisiert und in einer Decamersynthese angewendet. Das erhaltene Decamer wurde durch iterative Verwendung der Passerini‐Dreikomponenten‐Reaktion (P‐3CR) mit anschließender Entschützung hergestellt und trägt zehn unterschiedliche, wählbare Seitenketten. Dieser hocheffiziente Syntheseansatz ermöglichte exzellente Ausbeuten sowie die Synthese von perfekt sequenzdefinierten Makromolekülen im Multigramm‐Maßstab. Am Ende der Synthese wurde ein Olefin als Seitenkette eingeführt, das eine Selbstmetathese‐Reaktion des Decamers und damit die Synthese eines sequenzdefinierten 20‐mers mit einem Molekulargewicht von 7046.40 g mol−1 ermöglichte. Die erhaltenen Oligomere wurden vollständig mittels NMR‐ und IR‐Spektroskopie, GPC, GPC‐ESI‐MS und Massenspektrometrie (FAB‐ und Orbitrap‐ESI‐MS) charakterisiert.
Temporal Control of Membrane Fusion through Photolabile PEGylation of Liposome Membranes
Authors: Kong Li , Askes Sven H. C. , Bonnet Sylvestre , Kros Alexander , Campbell Frederick 
Published: December 2015

AbstractMembrane fusion results in the transport and mixing of (bio)molecules across otherwise impermeable barriers. In this communication, we describe the temporal control of targeted liposome–liposome membrane fusion and contents mixing using light as an external trigger. Our method relies on steric shielding and rapid, photoinduced deshielding of complementary fusogenic peptides tethered to opposing liposomal membranes. In an analogous approach, we were also able to demonstrate precise spatiotemporal control of liposome accumulation at cellular membranes in vitro.
Zuverlässiges Schalten von Diarylethenen in beide Richtungen mithilfe von sichtbarem Licht
Authors: Fredrich Sebastian , Göstl Robert , Herder Martin , Grubert Lutz , Hecht Stefan 
Published: December 2015

AbstractEin Diarylethen‐Photoschalter wurde kovalent einmal konjugiert und einmal nichtkonjugiert mit zwei Triplett‐Sensibilisatoreinheiten verknüpft, und die resultierenden Verbindungen wurden auf ihre photochromen Eigenschaften untersucht. Im Unterschied zum ursprünglichen Diarylethen (ohne Sensibilisator) und dem Derivat mit gesättigter Bindung zeigt der konjugierte Photoschalter eine ausgezeichnete Ermüdungsresistenz bedingt durch die Anregung mit sichtbarem Licht und den effektiven Triplettenergietransfer vom Biacetylterminus zum Diarylethenkern. Aufgrund der ausgedehnten π‐Konjugation und des Ringschlusses über den Triplettzustand lassen sich unsere Diarylethene mit sichtbarem Licht in beide Richtungen effektiv und robust schalten.
Corannulen komprimiert in einem molekularen Käfig
Authors: Schmidt Bernd M. , Osuga Takafumi , Sawada Tomohisa , Hoshino Manabu , Fujita Makoto 
Published: December 2015

AbstractDurch Selbstorganisation erhaltene Käfigverbindungen können als molekulare Pressen genutzt werden. Die Komplexierung der schalenförmigen Verbindung Corannulen (C20H10) im Inneren des Käfigs erfolgt unter erheblicher Planarisierung des Gasts. Dies wird anhand von zwei Beispielen, der Einlagerung von Corannulen mit Naphthalindiimid und der Einlagerung von zwei Monobromcorannulenen, demonstriert. Die Änderung der Struktur wurde eindeutig durch Einkristallröntgenstrukturanalyse nachgewiesen.
B(C6F5)3: A Lewis Acid that Brings the Light to the Solid State
Authors: Hansmann Max M. , López‐Andarias Alicia , Rettenmeier Eva , Egler‐Lucas Carolina , Rominger Frank , Hashmi A. Stephen K. , Romero‐Nieto Carlos 
Published: December 2015

AbstractThe straightforward coordination of the Lewis acid B(C6F5)3 to classical, non‐emitting aldehydes results in solid‐state photoluminescence. Variation of the electronic properties of the carbonyl moieties lead to the modulation of the solid‐state emission colors, covering the entire visible spectrum with quantum yields up to 0.64. Steady‐state spectroscopy in combination with X‐ray diffraction analysis and DFT calculations confirm that intermolecular interactions between the Lewis adducts are responsible for the observed luminescence. Alteration of the latter interactions induces, moreover, remarkable solid‐state phenomena such as piezochromism. The versatility and simplicity of our approach facilitate the future development of solid‐state emitting materials.
A Scalable and High‐Yield Strategy for the Synthesis of Sequence‐Defined Macromolecules
Authors: Solleder Susanne C. , Zengel Deniz , Wetzel Katharina S. , Meier Michael A. R. 
Published: December 2015

AbstractThe efficient synthesis of a sequence‐defined decamer, its characterization, and its straightforward dimerization through self‐metathesis are described. For this purpose, a monoprotected AB monomer was designed and used to synthesize a decamer bearing ten different and selectable side chains by iterative Passerini three‐component reaction (P‐3CR) and subsequent deprotection. The highly efficient procedure provided excellent yields and allows for the multigram‐scale synthesis of such perfectly defined macromolecules. An olefin was introduced at the end of the synthesis, allowing the self‐metathesis reaction of the resulting decamer to provide a sequence‐defined 20‐mer with a molecular weight of 7046.40 g mol−1. The obtained oligomers were carefully characterized by NMR and IR spectroscopy, GPC and GPC coupled to ESI‐MS, and mass spectrometry (FAB and orbitrap ESI‐MS).
Switching Diarylethenes Reliably in Both Directions with Visible Light
Authors: Fredrich Sebastian , Göstl Robert , Herder Martin , Grubert Lutz , Hecht Stefan 
Published: December 2015

AbstractA diarylethene photoswitch was covalently connected to two small triplet sensitizer moieties in a conjugated and nonconjugated fashion and the photochromic performance of the resulting compounds was investigated. In comparison with the parent diarylethene (without sensitizers) and one featuring saturated linkages, the conjugated photoswitch offers superior fatigue resistance upon visible‐light excitation due to effective triplet energy transfer from the biacetyl termini to the diarylethene core. Our design makes it possible to switch diarylethenes with visible light in both directions in a highly efficient and robust fashion based on extending π‐conjugation and by‐product‐free ring‐closure via the triplet manifold.
Rheological properties of thermoresponsive nanocomposite hydrogels
Authors: Hosseini Hossein , Tenhu Heikki , Hietala Sami 
Published: December 2015

ABSTRACTHighly elastic and robust nanocomposite hydrogels based on N‐isopropylacrylamide (NIPAM) and cationic (3‐acrylamidopropyl) trimethylammonium chloride (AMPTMA) were synthesized by photopolymerization. Nanoscopic clay, laponite XLS, was added in the gels during the synthesis. The effect of a hydrophobic salt, lithium bis(trifluoromethane) sulfonimide (LiNTf2), and clay content on the viscoelastic properties, swelling ratio, and stiffness of the nanocomposite hydrogels were investigated as a function of temperature. Synthetic clay served as a multifunctional cross‐linker, producing hydrogels with enhanced elastic properties. Anionic NTf2 binds to the cationic comonomer units and significantly affected the viscoelasticity and thermal properties. DSC measurements showed that the volume phase transition temperature and its enthalpy changed with the clay content and with introducing the cationic comonomer (AMPTMA) in the PNIPAM network. With the addition of either laponite XLS or the comonomer and 5 mM solution of LiNTf2, a fourfold and fivefold increase in elastic modulus was obtained, respectively, compared to that of the homopolymer PNIPAM hydrogel. With increasing the temperature from 20 to 45°C for the copolymer gel with 10% AMPTMA in 5 mM LiNTf2, the elastic modulus grew 15 times larger. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43123.
Carbonized electrospun polyacrylonitrile nanofibers as highly sensitive sensors in structural health monitoring of composite structures
Authors: Alarifi Ibrahim M , Alharbi Abdulaziz , Khan WseeemS , Asmatulu Ramazan 
Published: December 2015

ABSTRACTElectrospun polyacrylonitrile (PAN) nanofibers were stabilized at 280°C for 1 h in an ambient condition, and then carbonized at 850°C in inert argon gas for additional 1 h in order to fabricate highly pure carbonous nanofibers for the development of highly sensitive sensors in structural health monitoring (SHM) of composite aircraft and wind turbines. This study manifests the real‐time strain response of the carbonized PAN nanofibers under various tensile loadings. The prepared carbon nanofibers were placed on top of the carbon fiber pre‐preg composite as a single layer. Using a hand lay‐up method, and then co‐cured with the pre‐preg composites in a vacuum oven following the curing cycle of the composite. The electric wires were connected to the top surface of the composite panels where the cohesively bonded conductive nanofibers were placed prior to the tensile and compression loadings in the grips of the tensile unit. The test results clearly showed that the carbonized electrospun PAN nanofibers on the carbon fiber composites were remarkably performed well. Even the small strain rates (e.g., 0.020% strain) on the composite panels were easily detected through voltage and resistance changes of the panels. The change in voltage can be mainly attributed to the breakage/deformation of the conductive network of the carbonized PAN nanofibers under the loadings. The primary goal of the present study is to develop a cost‐effective, lightweight, and flexible strain sensor for the SHM of composite aircraft and wind turbines. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43235.
Prevalence of Cervical Enamel Projection and Its Impact on Furcation Involvement in Mandibular Molars: A Cone‐Beam Computed Tomography Study in Koreans
Authors: Lim Hyun‐Chang , Jeon Seok‐Kyun , Cha Jae‐Kook , Lee Jung‐Seok , Choi Seong‐Ho , Jung Ui‐Won 
Published: December 2015

ABSTRACTThis study evaluated the prevalence of cervical enamel projections (CEPs) in mandibular molars, and analyzed the correlation between CEPs and furcation involvement (FI) based on cone‐beam computed tomography (CBCT) data in a Korean population. CBCT images obtained from March 2012 to August 2012 were analyzed. CEPs and FI on the buccal and lingual surface were classified in three‐dimensionally reconstructed images and cross‐sectional views, and the correlation between these two parameters was analyzed. In total, 982 teeth in 425 patients were analyzed. The overall prevalence rate of CEPs was 76% (71% and 27% on the buccal and lingual surfaces, respectively). Grade I CEPs were the most common, followed by CEPs of grades II and III. There was a statistically significant, but negligible correlation between the CEP grade and the degree of FI on the buccal and lingual surfaces. Within the limitations of this cross‐sectional study, a high prevalence of CEPs were found in a Korean population, but the role of CEPs in provoking FI appeared not to be decisive. Anat Rec, 299:379–384, 2016. © 2015 Wiley Periodicals, Inc.
A Bromo‐Functionalized Conjugated Polymer as a Cross‐Linkable Anode Interlayer of Polymer Solar Cells
Authors: Meng Bin , Xie Zhiyuan , Liu Jun , Wang Lixiang 
Published: December 2015

AbstractA cross‐linkable conjugated polymer with bromo groups on the side chain has been developed and used as an anode interlayer to improve the active layer morphology and consequently enhance the device performance of polymer solar cells (PSCs). The polymer, PCDTBT‐Br, has cross‐linkable bromo groups attached to the side chain of a widely‐used donor polymer, poly[N‐9‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4,7‐di‐2‐thienyl‐2,1,3‐benzothiadiazole)] (PCDTBT). The pendant bromo groups do not significantly change the LUMO/HOMO energy levels and absorption spectrum of the PCDTBT polymer backbone. PDCTBT‐Br can crosslink under UV irradiation to give a robust film, which enables multilayer PSC device fabrication. Moreover, the much lower surface energy of PCDTBT‐Br (20.4 mJ m−2) compared to PEDOT:PSS (91.6 mJ m−2) is beneficial for achieving optimal active layer morphology. As a result, with PCDTBT:[6,6]‐phenyl‐C71 butyric acid methyl ester (PC71BM) as the active layer, the PSC device with PCDTBT‐Br as the underlying layer shows a power conversion efficiency (PCE) of 6.59 %, in comparison to a PCE of 5.86 % of the control device. The device performance enhancement is ascribed to the much improved phase separation with a fibrillar nanostructure in the active layer.