bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new solar signal: Average maximum sunspot magnetic fields independent of activity cycle
Authors: Livingston William , Watson Fraser 
Published: August 2015

AbstractOver the past 5 years, 2010 to April 2015, we observed 4176 sunspot umbrae in the infrared (IR) to measure maximum magnetic field strengths from the Zeeman splitting of Fe 15,648.5 Å. Herein we distinguish “field strengths” from “field flux.” Field strengths range from 1500 G in pores to 3500+ in large spots. We made one observation per spot per observing day, ignoring spot size. We show that in the IR no activity cycle dependence on average maximum field strength (2070 ± 20 G) has been found. A similar analysis of 17,450 spots observed in space by the Helioseismic and Magnetic Imager reveals a similar cycle independence (2050 ± 0.18 G). We conclude that the average maximum umbral fields are constant with time and independent of the activity cycle within our time coverage.
Characteristics of equatorial plasma bubble zonal drift velocity and tilt based on Hong Kong GPS CORS network: From 2001 to 2012
Authors: Ji Shengyue , Chen Wu , Weng Duojie , Wang Zhenjie 
Published: August 2015

AbstractHong Kong (22.3°N, 114.2°E, dip: 30.5°N; geomagnetic 15.7°N, 173.4°W, declination: 2.7°W) is a low‐latitude area, and the Hong Kong Continuously Operating Reference Station (CORS) network has been developed and maintained by Lands Department of Hong Kong government since 2001. Based on the collected GPS observations of a whole solar cycle from 2001 to 2012, a method is proposed to estimate the zonal drift velocity as well as the tilt of the observed plasma bubbles, and the estimated results are statistically analyzed. It is found that although the plasma bubbles are basically vertical within the equatorial plane, the tilt can be as big as more than 60° eastward or westward sometimes. And, the tilt and the zonal drift velocity are correlated. When the velocity is large, the tilt is also large generally. Another finding is that large velocity and tilt generally occur in spring and autumn and in solar active years.
Satellite estimates of precipitation susceptibility in low‐level marine stratiform clouds
Authors: Terai C. R. , Wood R. , Kubar T. L. 
Published: August 2015

AbstractQuantifying the sensitivity of warm rain to aerosols is important for constraining climate model estimates of aerosol indirect effects. In this study, the precipitation sensitivity to cloud droplet number concentration (Nd) in satellite retrievals is quantified by applying the precipitation susceptibility metric to a combined CloudSat/Moderate Resolution Imaging Spectroradiometer data set of stratus and stratocumulus clouds that cover the tropical and subtropical Pacific Ocean and Gulf of Mexico. Consistent with previous observational studies of marine stratocumulus, precipitation susceptibility decreases with increasing liquid water path (LWP), and the susceptibility of the mean precipitation rate R is nearly equal to the sum of the susceptibilities of precipitation intensity and of probability of precipitation. Consistent with previous modeling studies, the satellite retrievals reveal that precipitation susceptibility varies not only with LWP but also with Nd. Puzzlingly, negative values of precipitation susceptibility are found at low LWP and high Nd. There is marked regional variation in precipitation susceptibility values that cannot simply be explained by regional variations in LWP and Nd. This suggests other controls on precipitation apart from LWP and Nd and that precipitation susceptibility will need to be quantified and understood at the regional scale when relating to its role in controlling possible aerosol‐induced cloud lifetime effects.
Real‐time measurements of ambient aerosols in a polluted Indian city: Sources, characteristics, and processing of organic aerosols during foggy and nonfoggy periods
Authors: Chakraborty Abhishek , Bhattu Deepika , Gupta Tarun , Tripathi Sachchida N. , Canagaratna Manjula R. 
Published: August 2015

AbstractA detailed time‐resolved chemical characterization of ambient nonrefractory submicron aerosols (NR‐PM1) was conducted for the first time in India. The measurements were performed during the winter (November 2011 to January 2012) in a heavily polluted city of Kanpur, which is situated in the Indo‐Gangetic Plain. Real‐time measurements provided new insights into the sources and evolution of organic aerosols (OA) that could not be obtained using previously deployed filter‐based measurements at this site. The average NR‐PM1 loading was very high (>100 µg/m3) throughout the study, with OA contributing approximately 70% of the total aerosol mass. Source apportionment of the OA using positive matrix factorization revealed large contributions from fresh and aged biomass burning OA throughout the entire study period. A back trajectory analysis showed that the polluted air masses were affected by local sources and distant source regions where the burning of paddy residues occurs annually during winter. Several fog episodes were encountered during the study, and the OA composition varied between foggy and nonfoggy periods, with higher oxygen to carbon (O/C) ratios during the foggy periods. The evolution of OA and their elemental ratios (O:C and H:C) were investigated for the possible effects of fog processing.
Prediction of annual joint rain fade on EHF networks by weighted rain field selection
Authors: Paulson K. S. , Chinda I. D. 
Published: August 2015

AbstractWe present a computationally efficient method to predict joint rain fade on arbitrary networks of microwave links. Methods based on synthetic rain fields composed of a superposition of rain cells have been shown to produce useful predictions of joint fade, with low computational overhead. Other methods using rain fields derived from radar systems have much higher computational overhead but provide better predictions. The proposed method combines the best features of both methods by using a small number of measured rain fields to produce annual fade predictions. Rain fields are grouped into heavy rain and light rain groups by maximum rain rate. A small selection of rain fields from each group are downscaled and fade predictions generated by pseudointegration of specific attenuation. This paper presents a method to optimize the weights used to combine the heavy rain and light rain fade predictions to yield an estimate of the average annual distribution. The algorithm presented yields estimates of average annual fade distributions with an error small compared to year‐to‐year variation, using only 0.2% of the annual data set of rain fields.
Systemic Fluorescence Imaging of Zebrafish Glycans with Bioorthogonal Chemistry
Authors: Agarwal Paresh , Beahm Brendan J. , Shieh Peyton , Bertozzi Carolyn R. 
Published: August 2015

AbstractVertebrate glycans constitute a large, important, and dynamic set of post‐translational modifications that are notoriously difficult to manipulate and image. Although the chemical reporter strategy has been used in conjunction with bioorthogonal chemistry to image the external glycosylation state of live zebrafish and detect tumor‐associated glycans in mice, the ability to image glycans systemically within a live organism has remained elusive. Here, we report a method that combines the metabolic incorporation of a cyclooctyne‐functionalized sialic acid derivative with a ligation reaction of a fluorogenic tetrazine, allowing for the imaging of sialylated glycoconjugates within live zebrafish embryos.
Design of Highly Photofunctional Porous Polymer Films with Controlled Thickness and Prominent Microporosity
Authors: Gu Cheng , Huang Ning , Wu Yang , Xu Hong , Jiang Donglin 
Published: August 2015

AbstractPorous organic polymers allow the integration of various π‐units into robust porous π‐networks, but they are usually synthesized as unprocessable solids with poor light‐emitting performance as a result of aggregation‐related excitation dissipation. Herein, we report a general strategy for the synthesis of highly emissive photofunctional porous polymer films on the basis of a complementary scheme for the structural design of aggregation‐induced‐emissive π‐systems. We developed a high‐throughput and facile method for the direct synthesis of large‐area porous thin films at the liquid–electrode interface. The approach enables the preparation of microporous films within only a few seconds or minutes and allows precise control over their thickness with sub‐nanometer precision. By virtue of rapid photoinduced electron transfer, the thin films can detect explosives with enhanced sensitivity to low parts‐per‐million levels in a selective manner.
Carbon Dioxide Fixation and Sulfate Sequestration by a Supramolecular Trigonal Bipyramid
Authors: Browne Colm , Ramsay William J. , Ronson Tanya K. , Medley‐Hallam John , Nitschke Jonathan R. 
Published: August 2015

AbstractThe subcomponent self‐assembly of a bent dialdehyde ligand and different cationic and anionic templates led to the formation of two new metallosupramolecular architectures: a FeII4L6 molecular rectangle was isolated following reaction of the ligand with iron(II) tetrafluoroborate, and a M5L6 trigonal bipyramidal structure was constructed from either zinc(II) tetrafluoroborate or cadmium(II) trifluoromethanesulfonate. The spatially constrained arrangement of the three equatorial metal ions in the M5L6 structures was found to induce small‐molecule transformations. Atmospheric carbon dioxide was fixed as carbonate and bound to the equatorial metal centers in both the Zn5L6 and Cd5L6 assemblies, and sulfur dioxide was hydrated and bound as the sulfite dianion in the Zn5L6 structure. Subsequent in situ oxidation of the sulfite dianion resulted in a sulfate dianion bound within the supramolecular pocket.
μ‐PbSe: ein schweres CO‐Homolog als ungewöhnlicher Ligand
Authors: Thiele Günther , Franzke Yannick , Weigend Florian , Dehnen Stefanie 
Published: August 2015

AbstractAus Reaktionen von [K(18‐Krone‐6)]2[Pb2Se3] oder [K([2.2.2]crypt)]2[Pb2Se3] mit [Rh(PPh3)3Cl] in en (Ethan‐1,2‐diamin) gingen ionische Verbindungen mit den Anionen [Rh3(PPh3)6(μ3‐Se)2]− bzw. [Rh3(CN)2(PPh3)4(μ3‐Se)2(μ‐PbSe)]3− hervor. Letzteres enthält einen PbSe‐Liganden, ein sehr ungewöhnliches Homolog von CO, das als μ‐Brückenligand zwischen zwei Rh‐Atomen fungiert. Quantenchemische Rechnungen zeigen eine deutlich größere Bindungsenergie für PbSe als für CO, was auf die besser passende Größe der Ligandenorbitale, die recht starren Rh‐Se‐Rh‐Winkel und den daraus resultierenden Rh⋅⋅⋅Rh‐Abstand zurückgeführt wird. Um die abgewinkelte Koordination des Liganden nachzuvollziehen, wurden Orbitale mit signifikanten Liganden‐Beiträgen und deren Abhängigkeit vom Bindungswinkel einer genauen Studie unterzogen.
A Divergent Enantioselective Strategy for the Synthesis of Griseusins
Authors: Zhang Yinan , Ye Qing , Wang Xiachang , She Qing‐Bai , Thorson Jon S. 
Published: August 2015

AbstractThe first enantioselective total synthesis of griseusin A, griseusin C, 4′‐deacetyl‐griseusin A, and two non‐native counterparts in 11–14 steps is reported. This strategy highlights a key hydroxy‐directed CH olefination of 1‐methylene isochroman with an α,β‐unsaturated ketone followed by subsequent stereoselective epoxidation and regioselective cyclization to afford the signature tetrahydro‐spiropyran ring. Colorectal cancer cell cytotoxicities of the final products highlight the impact of the griseusin tetrahydro‐spiropyran ring on bioactivity. As the first divergent enantioselective synthesis, the strategy put forth sets the stage for further griseusin mechanism‐of‐action and SAR studies.
Ruthenium‐Catalyzed O‐ to S‐Alkyl Migration: A Pseudoreversible Barton–McCombie Pathway
Authors: Mahy William , Plucinski Pawel , Jover Jesús , Frost Christopher G. 
Published: August 2015

AbstractA practical ruthenium‐catalyzed O‐ to S‐alkyl migration affords structurally diverse thiooxazolidinones in excellent yields. Our studies suggest this catalytic transformation proceeds through a pseudoreversible radical pathway drawing mechanistic parallels to the classic Barton–McCombie reaction.
Ultrathin Co3S4 Nanosheets that Synergistically Engineer Spin States and Exposed Polyhedra that Promote Water Oxidation under Neutral Conditions
Authors: Liu Youwen , Xiao Chong , Lyu Mengjie , Lin Yue , Cai Weizheng , Huang Pengcheng , Tong Wei , Zou Youming , Xie Yi 
Published: August 2015

AbstractDevelopment of efficient and affordable electrocatalysts in neutral solutions is paramount importance for the renewable energy. Herein, we report that the oxygen evolution reaction (OER) performance of Co3S4 under neutral conditions can be enhanced by exposed octahedral planes and self‐adapted spin states in atomically thin nanosheets. A HAADF image clearly confirmed that the active octahedra with Jahn–Teller distortions were exposed exclusively. Most importantly, in the atomically thin nanosheets, the spin states of Co3+ in the octahedral self‐adapt from low‐spin to high‐spin states. As a result, the synergistic effect endow the Co3S4 nanosheets with superior OER performance, with exceptional low onset overpotentials of circa 0.31 V in neutral solutions, which is state‐of‐the‐art among inorganic non‐noble metal compounds.
Formation of C(sp2)Boronate Esters by Borylative Cyclization of Alkynes Using BCl3
Authors: Warner Andrew J. , Lawson James R. , Fasano Valerio , Ingleson Michael J. 
Published: August 2015

AbstractBCl3 is an inexpensive electrophile which induces the borylative cyclization of a wide range of substituted alkynes to regioselectively form polycycles containing synthetically versatile C(sp2)boronate esters. It proceeds rapidly, with good yields and is compatible with a range of functional groups and substitution patterns. Intermolecular 1,2‐carboboration of alkynes is also achieved using BCl3 to generate trisubstituted vinyl boronate esters.
Finely Tuned Polymer Interlayers Enhance Solar Cell Efficiency
Authors: Liu Yao , Page Zachariah A. , Russell Thomas P. , Emrick Todd 
Published: August 2015

AbstractThree conjugated polymer zwitterions (CPZs), containing thiophene‐, diketopyrrolopyrrole‐ (DPP), and naphthalene diimide (NDI) backbones, were synthesized with pendant zwitterions, specifically sulfobetaine groups. Diboronate‐ester‐functionalized bithiophene and benzothiadiazole monomers were copolymerized with zwitterion‐substituted dibromothiophene, DPP, and NDI monomers by A2+B2 Suzuki polymerization. The CPZs were incorporated into polymer solar cells (PSCs) as interlayers between the photoactive layer and Ag cathode. The thiophene‐based CPZs gave power conversion efficiencies (PCEs) of about 5 %, while the narrow‐energy‐gap DPP‐ and NDI‐based CPZs performed exceptionally well, giving PCEs of 9.49 % and 10.19 %, respectively. The interlayer thickness had only a minor impact on the device performance for the DPP‐ and NDI‐CPZs, a finding attributed to their electron‐transport properties. Ultraviolet photoelectron and reflectance spectroscopies, combined with external quantum efficiency measurements, provided structure–property relationships that lend insight into the function of CPZ interlayers in PSCs. NDI‐based CPZ interlayers provide some of the best performing organic solar cells reported to date, and prove useful in conjunction with high‐performing polymer‐active layers and stable, high‐work‐function, metal cathodes.
Palladium(II)‐Catalyzed Allylic CH Oxidation of Hindered Substrates Featuring Tunable Selectivity Over Extent of Oxidation
Authors: Xing Xiangyou , O'Connor Nicholas R. , Stoltz Brian M. 
Published: August 2015

AbstractThe use of Oxone and a palladium(II) catalyst enables the efficient allylic CH oxidation of sterically hindered α‐quaternary lactams which are unreactive under known conditions for similar transformations. This simple, safe, and effective system for CH activation allows for unusual tunable selectivity between a two‐electron oxidation to the allylic acetates and a four‐electron oxidation to the corresponding enals, with the dominant product depending on the presence or absence of water. The versatile synthetic utility of both the allylic acetate and enal products accessible through this methodology is also demonstrated.
Frontoparietal Bone in Extinct Palaeobatrachidae (Anura): Its Variation and Taxonomic Value
Authors: Roček Zbyněk , Boistel Renaud , Lenoir Nicolas , Mazurier Arnaud , Pierce Stephanie E. , Rage Jean‐Claude , Smirnov Sergei V. , Schwermann Achim H. , Valentin Xavier , Venczel Márton , Wuttke Michael , Zikmund Tomáš 
Published: August 2015

ABSTRACTPalaeobatrachidae are extinct frogs from Europe closely related to the Gondwanan Pipidae, which includes Xenopus. Their frontoparietal is a distinctive skeletal element which has served as a basis for establishing the genus Albionbatrachus. Because little was known about developmental and individual variation of the frontoparietal, and its usefulness in delimiting genera and species has sometimes been doubted, we investigate its structure in Palaeobatrachus and Albionbatrachus by means of X‐ray high resolution computer tomography (micro‐CT). To infer the scope of variation present in the fossil specimens, we also examined developmental and interspecific variation in extant Xenopus. In adults of extinct taxa, the internal structure of the frontoparietal bone consists of a superficial and a basal layer of compact bone, with a middle layer of cancellous bone between them, much as in early amphibians. In Albionbatrachus, the layer of cancellous bone, consisting of small and large cavities, was connected with the dorsal, sculptured surface of the bone by a system of narrow canals; in Palaeobatrachus, the layer of cancellous bone and the canals connecting this layer with the dorsal surface of the frontoparietal were reduced. The situation in Palaeobatrachus robustus from the lower Miocene of France is intermediate—while external features support assignment to Palaeobatrachus, the inner structure is similar to that in Albionbatrachus. It may be hypothesized that sculptured frontoparietals with a well‐developed layer of cancellous (i.e., vascularized) bone may indicate adaptation to a more terrestrial way of life, whereas a reduced cancellous layer might indicate a permanent water dweller. Anat Rec, 298:1848–1863, 2015. © 2015 Wiley Periodicals, Inc.
A rapid UPLC‐MS/MS method for the determination of oleanolic acid in rat plasma and liver tissue: application to plasma and liver pharmacokinetics
Authors: Li Tian‐xue , Chu Chao‐sen , Zhu Jia‐yu , Yang Tian‐yi , Zhang Jie , Hu Yu‐tao , Yang Xing‐hao 
Published: August 2015

AbstractA reliable high‐throughput ultra‐high performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method was developed and validated for oleanolic acid (OA) determination in rat plasma and liver tissue using glycyrrhetic acid as the internal standard (IS). Plasma and liver homogenate samples were prepared using solid‐phase extraction. Chromatographic separation was achieved on a C18 column using an isocratic mobile phase system. The detection was performed by multiple reaction monitoring mode via positive electrospray ionization interface. The calibration curves showed good linearity (R2 > 0.9997) within the tested concentration ranges. The lower limit of quantification for plasma and liver tissue was ≤0.75 ng/mL. The intra‐ and inter‐day precision and accuracy deviations were within ±15% in plasma and liver tissue. The mean extraction recoveries ranged from 80.8 to 87.0%. In addition, the carryover, matrix effect, stability and robustness involved in the method were also validated. The method was successfully applied to the plasma and hepatic pharmacokinetics of OA after oral administration to rats. Copyright © 2015 John Wiley & Sons, Ltd.
Discovery and Characterization of New Hydroxamate Siderophores, Baumannoferrin A and B, produced by Acinetobacter baumannii
Authors: Penwell William F. , DeGrace Nancy , Tentarelli Sharon , Gauthier Lise , Gilbert Catherine M. , Arivett Brock A. , Miller Alita A. , Durand‐Reville Thomas F. , Joubran Camil , Actis Luis A. 
Published: August 2015

AbstractAcinetobacter baumannii AYE does not produce acinetobactin but grows under iron limitation. Accordingly, analyses of AYE iron‐restricted culture supernatants resulted in the isolation of two fractions, which contained only hydroxamates and showed siderophore activity. Structural analyses identified baumannoferrin A and baumannoferrin B, which differ only by a double bond. These siderophores are composed of citrate, 1,3‐diaminopropane, 2,4‐diaminobutyrate, decenoic acid, and α‐ketoglutarate. Analysis of the AYE genome showed the presence of a 12‐gene cluster coding for proteins similar to those involved in the production and utilization of the hydroxamate siderophores acinetoferrin and achromobactin. As A. baumannii AYE does not produce acinetobactin and harbors only one gene cluster encoding the production and utilization of a siderophore, this strain's growth under iron limitation depends on baumannoferrin, a novel hydroxamate that could play a role in its virulence.
Microreactors as a Tool for Acquiring Kinetic Data on Photochemical Reactions
Authors: Aillet Tristan , Loubière Karine , Dechy‐Cabaret Odile , Prat Laurent 
Published: August 2015

AbstractFor the first time, the application of microreactors as a tool for acquiring kinetic data on a photochemical reaction is demonstrated. For illustration, a T‐photochromic system is considered. By using modeling tools and carrying out specific experiments in a spiral‐shaped microreactor irradiated by an ultraviolet/light‐emitting diode (UV‐LED) array, the two kinetic parameters of the reaction, namely, quantum yield and rate of thermal back reaction, are determined. Once these parameters are known, the photochromic reaction is performed in two other microreactors in order to investigate a wider range of operating conditions. It is observed that a critical residence time exists beyond which the conversion into the open form decreases due to a decomposition reaction. The value of the critical residence depends on the microreactor type, which can be predicted by applying the model developed.
Synthesis and Atropisomerism of Cascaded Tetraphenylporphyrin–[60]Fullerene Hybrids
Authors: Schlundt Sebastian , Bauer Walter , Hirsch Andreas 
Published: August 2015

AbstractFlexible, linked dendritic tetraphenylporphyrin (TPP)–fullerene hybrids were synthesized. They were designed to gain insight into and mimic the primary events in the natural photosynthetic reaction center. These multiporphyrin moieties are based on a light‐harvesting concept. Moreover, they incorporate multiple redox components aligned along a redox gradient. Newkome‐type dendrons were added to these TPP–fullerene hybrids. In principle they can mediate pH‐dependent water solubility, which, however, could not be observed in this case. A protecting‐group strategy using tert‐butyldiphenylsilyl groups allows convergent synthesis of the dendritic compounds. The dendritic multiporphyrins were synthesized separately and can be used as individual building blocks. Atropisomerism was observed in the dendritic compounds, and single atropisomers could be assigned to the corresponding peaks of a characteristic pattern in the NMR spectra. Deprotection of the Newkome‐type dendrons was shown to be feasible under mild conditions that leave the redox gradient intact.