bluuebunny/crossref_metadata_2025_split huggingface dataset:
Testing linear theory of EMIC waves in the inner magnetosphere: Cluster observations
Authors: Lin R.‐L. , Zhang J.‐C. , Allen R. C. , Kistler L. M. , Mouikis C. G. , Gong J.‐C. , Liu S.‐Q. , Shi L.‐Q. , Klecker B. , Sauvaud J.‐A. , Dunlop M. W. 
Published: January 2014

AbstractIn this paper, we test whether time periods with hot proton temperature anisotropy are associated with electromagnetic ion cyclotron (EMIC) waves and whether the plasma conditions during the observed waves satisfy the linear theory threshold condition. We identify 865 events observed by the Composition Distribution Function instrument onboard Cluster spacecraft 4 during 1 January 2001 to 1 January 2011 that exhibit a positive temperature anisotropy (Ahp = T⊥ h/T∥ h − 1) in the 10–40 keV protons. The events occur over an L range from 4 to 10 in all magnetic local times and at magnetic latitudes (MLATs) within ±50°. Of these hot proton temperature anisotropy (HPTA) events, only 68 events have electromagnetic ion cyclotron (EMIC) waves. In these 68 HPTA events, for those at 3.8<L ≤ 5 and |MLAT| ≤ 10°, the EMIC waves with powers >1.0 nT2/Hz mainly appear in the region with fEMIC/fH,eq < 0.8. Two stop bands are present, one near the region with fEMIC/fH,eq ≈ 0.33, the other in the region with 0.8 < fEMIC/fH,eq < 0.9. Most of the EMIC waves in the He, H, and >H bands satisfy Ahp/(Ahp + 1) > fEMIC/fH,lo, Ahp/(Ahp + 1) > 0.45  × fEMIC/fH,lo, and Ahp/(Ahp + 1) < 0.45  × fEMIC/fH,lo. fEMIC,  fH,eq, and fH,lo are the EMIC wave frequency, the magnetic equatorial, and the local proton gyrofrequencies. We also find that the EMIC waves predominantly occur with Ahp > 0.25. By testing a threshold equation for the EMIC instability based on linear theory, we find that for EMIC waves with |MLAT| ≤ 10° in the He, H, and >H bands, the percentages that satisfy the predicted conditions for wave growth by the threshold equation are 15.2%, 24.6%, and 25.6%. For the EMIC waves with |MLAT| > 10° the percentages that satisfy the wave growth predicted conditions are only 2.8%, 2.6%, and 0.0%. Finally, possible reasons for the low forecast accuracies of EMIC waves are suggested.
Magnetotelluric investigations of the lithosphere beneath the central Rae craton, mainland Nunavut, Canada
Authors: Spratt Jessica E. , Skulski Thomas , Craven James A. , Jones Alan G. , Snyder David B. , Kiyan Duygu 
Published: January 2014

AbstractNew magnetotelluric soundings at 64 locations throughout the central Rae craton on mainland Nunavut constrain 2‐D resistivity models of the crust and lithospheric mantle beneath three regional transects. Responses determined from colocated broadband and long‐period magnetotelluric recording instruments enabled resistivity imaging to depths of > 300 km. Strike analysis and distortion decomposition on all data reveal a regional trend of 45–53°, but locally the geoelectric strike angle varies laterally and with depth. The 2‐D models reveal a resistive upper crust to depths of 15–35 km that is underlain by a conductive layer that appears to be discontinuous at or near major mapped geological boundaries. Surface projections of the conductive layer coincide with areas of high grade, Archean metasedimentary rocks. Tectonic burial of these rocks and thickening of the crust occurred during the Paleoproterozoic Arrowsmith (2.3 Ga) and Trans‐Hudson orogenies (1.85 Ga). Overall, the uppermost mantle of the Rae craton shows resistivity values that range from ~3000 Ω m in the northeast (beneath Baffin Island and the Melville Peninsula) to ~10,000 Ω m beneath the central Rae craton, to >50,000 Ω m in the south near the Hearne Domain. Near‐vertical zones of reduced resistivity are identified within the uppermost mantle lithosphere that may be related to areas affected by mantle melt or metasomatism associated with emplacement of Hudsonian granites. A regional decrease in resistivities to values of ~500 Ω m at depths of 180–220 km, increasing to 300 km near the southern margin of the Rae craton, is interpreted as the lithosphere‐asthenosphere boundary.
Antigorite‐induced seismic anisotropy and implications for deformation in subduction zones and the Tibetan Plateau
Authors: Shao Tongbin , Ji Shaocheng , Kondo Yosuke , Michibayashi Katsuyoshi , Wang Qian , Xu Zhiqin , Sun Shengsi , Marcotte Denis , Salisbury Matthew H. 
Published: January 2014

AbstractThe present study, which is a follow‐up of the Journal of Geophysical Research paper by Ji et al. (2013a), provides a new calibration for both seismic and fabric properties of antigorite serpentinites. Comparisons of the laboratory velocities of antigorite serpentinites measured at high pressures with crystallographic‐preferred orientation data measured using electron backscatter diffraction techniques demonstrate that seismic anisotropy in high T serpentinite, which is essentially controlled by the antigorite c axis fabric, is independent on the operating slip system but strongly dependent on the regime and magnitude of finite strain experienced by the rock. Extrapolation of the experimental data with both pressure and temperature suggests that Vp anisotropy decreases but shear wave splitting (ΔVs) and Vp/Vs increase with increasing pressure in either cold or hot subduction zones. For a cold, steeply subducting slab, antigorite is most likely deformed by nearly coaxial flattening or trench‐parallel movements, forming trench‐parallel seismic anisotropy. For a hot, shallowly subducting slab, however, antigorite is most likely deformed by simple shear or transpression. Trench‐normal seismic anisotropy can be observed when the subducting dip angle is smaller than 30°. The geophysical characteristics of the Tibetan Plateau such as strong heterogeneity in Vp, Vs and attenuation, shear wave splitting and electric conductivity may be explained by the presence of strongly deformed serpentinites in lithospheric shear zones reactivated along former suture zones between amalgamated blocks, hydrated zones of subducting lithospheric mantle, and the crust‐mantle boundary if the temperature is below 700°C in the region of interest.
Diagnosing shortwave cryosphere radiative effect and its 21st century evolution in CESM
Authors: Perket Justin , Flanner Mark G. , Kay Jennifer E. 
Published: January 2014

AbstractWe incorporate a new diagnostic called the cryosphere radiative effect (CrRE), the instantaneous influence of surface snow and sea ice on the top‐of‐model solar energy budget, into two released versions of the Community Earth System Model (CESM1 and CCSM4). CrRE offers a more climatically relevant metric of the cryospheric state than snow and sea ice extent and is influenced by factors such as the seasonal cycle of insolation, cloud masking, and vegetation cover. We evaluate CrRE during the late 20th century and over the 21st century, specifically diagnosing the nature of CrRE contributions from terrestrial and marine sources. The radiative influence of ice sheets and glaciers is not considered, but snow on top of them is accounted for. Present‐day global CrRE in both models is −3.8 W m−2, with a boreal component (−4.2 to −4.6 W m−2) that compares well with observationally derived estimates (−3.9 to −4.6 W m−2). Similar present‐day CrRE in the two model versions results from compensating differences in cloud masking and sea ice extent. Over the 21st century, radiative forcing in the Representative Concentration Pathway (RCP) 8.5 scenario causes reduced boreal sea ice cover, austral sea ice cover, and boreal snow cover, which all contribute roughly equally to enhancing global absorbed shortwave radiation by 1.4–1.8 Wm−2. Twenty‐first century RCP8.5 global cryospheric albedo feedback are +0.41 and +0.45 W/m2/K, indicating that the two models exhibit similar temperature‐normalized CrRE change.
Rapid Formation of a Monolayer of Oriented Hard‐Magnetic Strontium Hexaferrite Nanoparticles on a Solid Substrate
Authors: Kushnir Sergey E. , Koshkodaev Dmitry S. , Kazin Pavel E. , Zuev Dmitry M. , Zaytsev Dmitry D. , Jansen Martin 
Published: January 2014

AbstractSingle crystal nanoplatelets of M‐type strontium hexaferrite, which were prepared by oxide glass crystallization, form colloidal solutions after consequent leaching and peptization of the nanocrystalline material. The colloids are stabilized by the particles charging to a zeta‐potential of about 50 mV. Monolayers of oriented platelet strontium hexaferrite nanoparticles form readily on a glass surface while immersing the substrate in the colloidal solution due to Columb attraction of the positively charged nanoparticles to the negatively charged surface. The films show almost rectangular magnetization hysteresis loops typical for strongly textured hard‐magnetic material.
Foldable Textile Electronic Devices Using All‐Organic Conductive Fibers
Authors: Miura Hiroaki , Fukuyama Yasuhiro , Sunda Takashi , Lin Bangjia , Zhou Jian , Takizawa Junko , Ohmori Akio , Kimura Mutsumi 
Published: January 2014

AbstractScalable conductive multifilament of poly(3,4‐ethylenedioxythiophene) doped with poly(4‐styrene sulfonate) (PEDOT:PSS) and poly(vinyl alcohol) (PVA) was fabricated by a coagulation of spinning dope solution in cold methanol. The multifilament was composed of uniform circular fibers with an average diameter of 60 ± 5 μm and showed good enough mechanical properties for textile processes while maintaining electronic conductivity. The PEDOT:PSS/PVA blended fibers displayed an actuation response when a voltage was applied in air and the foldable textiles based on the PEDOT:PSS/PVA blended fibers worked as flexible electrodes to detect human heartbeats. The organic conductive fibers can be a platform for lightweight wearable electronics.
Synthesis of Spiro[chroman/tetrahydrothiophene‐3,3′‐oxindole] ScaffoldsviaHeteroatom‐Michael–Michael Reactions: Easily Controlled EnantioselectivityviaBifunctional Catalysts
Authors: Huang Youming , Zheng Changwu , Chai Zhuo , Zhao Gang 
Published: January 2014

AbstractAn efficient method for the construction of chiral spirooxindole‐chroman and spirooxindole‐tetrahydrothiophene scaffolds with three consecutive chiral centers including an all‐carbon quaternary spirocenter has been developed. This method features an asymmetric thia/oxa‐Michael–Michael cascade sequence in a single operation in the presence of chiral tertiary amine‐thioureas as the catalysts, providing the desired products in good chemical yields and optical purities.magnified image
Copper‐Catalyzed Decarboxylative CN Triple Bond Formation: Direct Synthesis of Benzonitriles from Phenylacetic Acids Under O2 Atmosphere
Authors: Feng Qiang , Song Qiuling 
Published: January 2014

AbstractA copper‐catalyzed reaction of phenylacetic acids with urea was found to afford benzonitriles under an oxygen atmosphere. This reaction proceeds smoothly by a sequence of decarboxylation, dioxygen activation, CH bond functionalization, and nitrile formation with urea as the nitrogen source. Molecular oxygen was found to play a crucial role in this transformation. This reaction represents a novel protocol for the formation of benzonitriles in an environmental friendly way and with good functional group tolerability.magnified image
Fluorine in Shark Teeth: Its Direct Atomic‐Resolution Imaging and Strengthening Function
Authors: Chen Chunlin , Wang Zhongchang , Saito Mitsuhiro , Tohei Tetsuya , Takano Yoshiro , Ikuhara Yuichi 
Published: January 2014

AbstractAtomic‐resolution imaging of beam‐sensitive biominerals is extremely challenging, owing to their fairly complex structures and the damage caused by electron irradiation. Herein, we overcome these difficulties by performing aberration‐corrected electron microscopy with low‐dose imaging techniques, and report the successful direct atomic‐resolution imaging of every individual atomic column in the complex fluorapatite structure of shark tooth enameloid, which can be of paramount importance for teeth in general. We demonstrate that every individual atomic column in shark tooth enameloid can be spatially resolved, and has a complex fluorapatite structure. Furthermore, ab initio calculations show that fluorine atoms can be covalently bound to the surrounding calcium atoms, which improves understanding of their caries‐reducing effects in shark teeth.
Die Existenz von Hexafluorarsen(V)‐säure
Authors: Axhausen Joachim , Lux Karin , Kornath Andreas 
Published: January 2014

AbstractDie homogene Mischung von wasserfreiem Fluorwasserstoff und Antimonpentafluorid, aHF/AsF5, ist als supersaures System bekannt. Die hohe Säurestärke wird durch die Bildung von [H2F]+ [AsF6]− erklärt. Es gibt keine experimentellen Belege für die Existenz des freien Säuremoleküls HAsF6. Wir haben die Reaktion von Trimethylsilyl‐N,N‐dimethylcarbamat im binären System aHF/AsF5 untersucht und beobachteten die Zersetzung von Trimethylsilyl‐N,N‐dimethylcarbamat bei −50 °C in Dimethylammoniumhexafluoridoarsenat und eine Cokristallisation von HAsF6. Eine Einkristallröntgenstrukturanalyse zeigt ein HAsF6‐Molekül, das eine unsymmetrische Wasserstoffbrücke zu einem Hexafluoridoarsenat‐Anion bildet. Aufgrund der nicht berechenbaren Situation im Kristallgitter wird die Molekülstruktur von HAsF6 durch quantenchemische Strukturoptimierung der beiden Extremfälle [FHF‐AsF5] (starke Wasserstoffbrücke) und HAsF6 (keine Wasserstoffbrücke) auf PBE1PBE/6‐311G(3df,3pd)‐Niveau berechnet.
Rational Perturbation of the Fluorescence Quantum Yield in Emission‐Tunable and Predictable Fluorophores (Seoul‐Fluors) by a Facile Synthetic Method Involving CH Activation
Authors: Choi Eun Joung , Kim Eunha , Lee Youngjun , Jo Ala , Park Seung Bum 
Published: January 2014

AbstractFluorescence imaging enables the uniquely sensitive observation of functional‐ and molecular‐recognition events in living cells. However, only a limited range of biological processes have been subjected to imaging because of the lack of a design strategy and difficulties in the synthesis of biosensors. Herein, we report a facile synthesis of emission‐tunable and predictable Seoul‐Fluors, 9‐aryl‐1,2‐dihydrolopyrrolo[3,4‐b]indolizin‐3‐ones, with various R1 and R2 substituents by coinage‐metal‐catalyzed intramolecular 1,3‐dipolar cycloaddition and subsequent palladium‐mediated CH activation. We also showed that the quantum yields of Seoul‐Fluors are controlled by the electronic nature of the substituents, which influences the extent of photoinduced electron transfer. On the basis of this understanding, we demonstrated our design strategy by the development of a Seoul‐Fluor‐based chemosensor 20 for reactive oxygen species that was not accessible by a previous synthetic route.
Xanthomonine I–III: eine neue Klasse von Lassopeptiden mit einem Makrolactamring aus sieben Aminosäureresten
Authors: Hegemann Julian D. , Zimmermann Marcel , Zhu Shaozhou , Steuber Holger , Harms Klaus , Xie Xiulan , Marahiel Mohamed A. 
Published: January 2014

AbstractLassopeptide gehören zu den ribosomal synthetisierten und posttranslatorisch modifizierten Peptiden. Ihr gemeinsames Erkennungsmerkmal ist ein N‐terminaler Makrolactamring, der von einem C‐terminalen Schwanz durchfädelt wird. Diese “Lassofaltung” wird durch sterische Wechselwirkungen aufrechterhalten. In dieser Studie werden die Isolierung und Charakterisierung der Xanthomonine I–III, der ersten Lassopeptide mit einem nur aus sieben Aminosäuren bestehenden Makrolactamring, sowie die Kristallstruktur von Xanthomonin I und die NMR‐spektroskopisch ermittelte Struktur von Xanthomonin II beschrieben. Insgesamt wurden 25 Xanthomonin‐II‐Varianten generiert, um Aspekte der Biosynthese, der Stabilisierung und der Aufrechterhaltug der Lassofaltung zu testen. Diese Mutagenesestudie offenbart die Einschränkungen, die ein so kleiner Ring für das Durchfädeln bedeutet, und zeigt, dass jede Stöpselaminosäure größer als Serin eine hitzestabile Lassofaltung in Xanthomonin II aufrechterhalten kann.
Flavoenzym‐katalysierte Bildung von Disulfidbrücken in Naturstoffen
Authors: Scharf Daniel H. , Groll Michael , Habel Andreas , Heinekamp Thorsten , Hertweck Christian , Brakhage Axel A. , Huber Eva M. 
Published: January 2014

AbstractDie Natur hält Verbindungen verschiedenster chemischer Struktur und biologischer Aktivität bereit, darunter schwefelhaltige Substanzen aus Bakterien und Pilzen. Einige dieser Stoffe enthalten ein Disulfid, das unabdingbar für ihre Bioaktivität ist. Spezielle Oxidoreduktasen wie GliT, HlmI und DepH katalysieren die Bildung dieses Disulfids im Virulenzfaktor Gliotoxin, dem Antibiotikum Holomycin bzw. dem Krebsmedikament Romidepsin. Alle drei Enzyme wurden mithilfe von Röntgenstrukturanalyse und Aktivitätstests untersucht. Trotz ihrer unterschiedlich großen Substrattaschen und ihrer verschiedenen Spezifitäten wird ein gemeinsamer Reaktionsmechanismus postuliert. Dieser basiert auf den erhaltenen Kristallstrukturen und wird durch Mutageneseexperimente gestützt.
Integrated Antimicrobial and Nonfouling Zwitterionic Polymers
Authors: Mi Luo , Jiang Shaoyi 
Published: January 2014

AbstractZwitterionic polymers are generally viewed as a new class of nonfouling materials. Unlike their poly(ethylene glycol) (PEG) counterparts, zwitterionic polymers have a broader chemical diversity and greater freedom for molecular design. In this Minireview, we highlight recent microbiological applications of zwitterionic polymers and their derivatives, with an emphasis on several unique molecular strategies to integrate antimicrobial and nonfouling properties. We will also discuss our insights into the bacterial nonfouling performance of zwitterionic polymers and one example of engineering zwitterionic polymer derivatives for antimicrobial wound‐dressing applications.
Quinones as Dienophiles in the Diels–Alder Reaction: History and Applications in Total Synthesis
Authors: Nawrat Christopher C. , Moody Christopher J. 
Published: January 2014

AbstractIn the canon of reactions available to the organic chemist engaged in total synthesis, the Diels–Alder reaction is among the most powerful and well understood. Its ability to rapidly generate molecular complexity through the simultaneous formation of two carboncarbon bonds is almost unrivalled, and this is reflected in the great number of reported applications of this reaction. Historically, the use of quinones as dienophiles is highly significant, being the very first example investigated by Diels and Alder. Herein, we review the application of the Diels–Alder reaction of quinones in the total synthesis of natural products. The highlighted examples span some 60 years from the landmark syntheses of morphine (1952) and reserpine (1956) by Gates and Woodward, respectively, through to the present day examples, such as the tetracyclines.
Xanthomonins I–III: A New Class of Lasso Peptides with a Seven‐Residue Macrolactam Ring
Authors: Hegemann Julian D. , Zimmermann Marcel , Zhu Shaozhou , Steuber Holger , Harms Klaus , Xie Xiulan , Marahiel Mohamed A. 
Published: January 2014

AbstractLasso peptides belong to the class of ribosomally synthesized and post‐translationally modified peptides. Their common distinguishing feature is an N‐terminal macrolactam ring that is threaded by the C‐terminal tail. This lasso fold is maintained through steric interactions. The isolation and characterization of xanthomonins I–III, the first lasso peptides featuring macrolactam rings consisting of only seven amino acids, is now presented. The crystal structure of xanthomonin I and the NMR structure of xanthomonin II were also determined. A total of 25 variants of xanthomonin II were generated to probe different aspects of the biosynthesis, stability, and fold maintenance. These mutational studies reveal the limits such a small ring imposes on the threading and show that every plug amino acid larger than serine is able to maintain a heat‐stable lasso fold in the xanthomonin II scaffold.
Rhodium(I)‐Catalyzed Decarbonylative Spirocyclization through CC Bond Cleavage of Benzocyclobutenones: An Efficient Approach to Functionalized Spirocycles
Authors: Xu Tao , Savage Nikolas A. , Dong Guangbin 
Published: January 2014

AbstractThe rhodium‐catalyzed formation of all‐carbon spirocenters involves a decarbonylative coupling of trisubstituted cyclic olefins and benzocyclobutenones through CC activation. The metal–ligand combination [{Rh(CO)2Cl}2]/P(C6F5)3 catalyzed this transformation most efficiently. A range of diverse spirocycles were synthesized in good to excellent yields and many sensitive functional groups were tolerated. A mechanistic study supports a hydrogen‐transfer process that occurs through a β‐H elimination/decarbonylation pathway.
Prevalence of venous thromboembolism at diagnosis of upper gastrointestinal cancer
Authors: Larsen A C , Dabrowski T , Frøkjær J B , Fisker R V , Iyer V V , Møller B K , Kristensen S R , Thorlacius-Ussing O 
Published: January 2014

Abstract

Background
Venous thromboembolism (VTE) in patients with upper gastrointestinal (GI) cancer increases morbidity and mortality. This study aimed to determine the prevalence of VTE at diagnosis of upper GI cancer.

Methods
Patients admitted between February 2008 and February 2011 with upper GI cancer (pancreatic, extrahepatic biliary, lower oesophageal, gastro-oesophageal junction or gastric cancer) were investigated in a cross-sectional cohort study. At cancer diagnosis, all patients were examined for deep vein thrombosis (DVT) by means of bilateral compression ultrasonography. From February 2009 and onwards, computed tomographic pulmonary angiography (CTPA) was also performed for the diagnosis of pulmonary embolism (PE).

Results
Some 250 patients had ultrasonography; CTPA was performed in 143 patients on admission. DVT was detected in 13 (5·2 per cent) of the 250 patients, eight (3·2 per cent) of whom were asymptomatic. DVT was correlated with tumour location in the pancreaticobiliary tract (odds ratio (OR) 6·27, 95 per cent confidence interval 1·18 to 33·38; P = 0·031) and tumour stage IV (OR 19·34, 2·33 to 160·70; P = 0·006). PE was detected in 11 (7·7 per cent) of 143 patients, eight (5·6 per cent) of whom were asymptomatic. PE embolism was also significantly more common in patients with pancreaticobiliary tract cancer (OR 7·81, 1·28 to 47·62; P = 0·026) and in those with stage IV disease (OR 17·19, 1·83 to 161·50; P = 0·013).

Conclusion
The prevalence of VTE at cancer diagnosis was significantly higher in patients with pancreaticobiliary tract cancer than in those with other forms of upper GI cancer, and in patients with advanced cancer stage.