bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of periodic variations in Saturn's magnetosphere by compressional waves
Authors: Kivelson Margaret Galland , Jia Xianzhe
Published: September 2014

Many of the periodic variations observed in Saturn's magnetosphere can be linked directly to the presence of a rotating pattern of field‐aligned currents that link the northern and southern ionospheres with each other and with the magnetosphere. Such a current system is incorporated in a magnetohydrodynamic simulation that has previously been shown to reproduce many of the observed periodic properties of the system. Here the simulation is used to investigate a range of phenomena that can be attributed to the effects of compressional waves launched from the rotating current sources. The compressional waves are found to drive the flapping of the plasma sheet and the expansion and contraction of the magnetopause in each rotation period. Because the compressional perturbations weaken as they rotate from morning to evening around the dayside of the magnetosphere, the boundary develops a strong morning‐evening asymmetry. A fit to the shape is provided that may be useful in further investigation of magnetopause properties, but there is already evidence of the proposed asymmetry in the observations of Clarke et al. (2010a).
Long‐term trends in thermospheric neutral temperature and density above Millstone Hill
Authors: Oliver W. L. , Holt J. M. , Zhang S.‐R. , Goncharenko L. P.
Published: September 2014

Incoherent scatter radar measurements of ionospheric temperature and density collected above Millstone Hill over the years 1976–2013 are analyzed to show the long‐term trends in noontime neutral temperature and neutral O density over the height region 120–500 km. Exospheric temperature cooled by 69.3 ± 6.4 K over the period, an order of magnitude greater than that expected from greenhouse gas action. The O density dropped 0.081 ± 5.6% at 400 km altitude but rose by 36.9 ± 5.0% at 120 km over this period. This trend in density at 400 km agrees with that determined from satellite drag. The increase in density at 120 km counteracts the thermal contraction of the thermosphere expected to be associated with the cooling, resulting in only a small density response at 400 km. The long‐term O density increase at 120 km may be caused by a long‐term descent of the turbopause height of 4.2 km. Such a descent has been documented by a series of rocket mass spectrometer measurements.
Pyrolysed 3D‐Carbon Scaffolds Induce Spontaneous Differentiation of Human Neural Stem Cells and Facilitate Real‐Time Dopamine Detection
Authors: Amato Letizia , Heiskanen Arto , Caviglia Claudia , Shah Fozia , Zór Kinga , Skolimowski Maciej , Madou Marc , Gammelgaard Lauge , Hansen Rasmus , Seiz Emma G. , Ramos Milagros , Moreno Tania Ramos , Martínez‐Serrano Alberto , Keller Stephan S. , Emnéus Jenny
Published: September 2014

Structurally patterned pyrolysed three‐dimensional carbon scaffolds (p3D‐carbon) are fabricated and applied for differentiation of human neural stem cells (hNSCs) developed for cell replacement therapy and sensing of released dopamine. In the absence of differentiation factors (DF) the pyrolysed carbon material induces spontaneous hNSC differentiation into mature dopamine‐producing neurons and the 3D‐topography promotes neurite elongation. In the presence and absence of DF, ≈73–82% of the hNSCs obtain dopaminergic properties on pyrolysed carbon, a to‐date unseen efficiency in both two‐dimensional (2D) and 3D environment. Due to conductive properties and 3D environment, the p3D‐carbon serves as a neurotransmitter trap, enabling electrochemical detection of a significantly larger dopamine fraction released by the hNSC derived neurons than on conventional 2D electrodes. This is the first study of its kind, presenting new conductive 3D scaffolds that provide highly efficient hNSC differentiation to dopaminergic phenotype combined with real‐time in situ confirmation of the fate of the hNSC‐derived neurons.
Phase Transitions and Anisotropic Thermal Expansion in High Mobility Core‐expanded Naphthalene Diimide Thin Film Transistors
Authors: Gann Eliot , Gao Xike , Di Chong‐an , McNeill Christopher R.
Published: September 2014

In situ grazing incidence wide‐angle X‐ray scattering (GIWAXS) is used to study the in situ thermal behavior of solution‐processed, high mobility core‐expanded naphthalene diimide thin films. A series of three different molecules is studied where the side‐chain branching position is systematically varied through the use of 2‐, 3‐ and 4‐branched N‐alkyl chains. For all molecules, a number of different phases and their associated phase transitions are observed with heating up to 200 °C. In situ GIWAXS measurements allow following significant variations of packing in each phase including crystalline coherence length, orientation, d‐spacing, and paracrystallinity, as well as, for the first time, thin film thermal expansion coefficients in both the in‐plane and out‐of‐plane direction. Relating these parameters with device measurements of quenched films, a striking correlation is found between high field‐effect mobilities and low in‐plane thermal expansion coefficients. This relationship indicates that high in‐plane thermal expansion coefficients are detrimental to in‐plane charge transport due to the formation of nanoscale defects in the critical first few monolayers upon quenching.
Over 1.1 eV Workfunction Tuning of Cesium Intercalated Metal Oxides for Functioning as Both Electron and Hole Transport Layers in Organic Optoelectronic Devices
Authors: Li Xinchen , Xie Fengxian , Zhang Shaoqing , Hou Jianhui , Choy Wallace C. H.
Published: September 2014

In this paper, over 1.1 eV continuous tuning of metal oxides workfunction is realized by cesium intercalation, making the metal oxide function as both electron transport layer and hole transport layer in organic optoelectronic devices. The demonstrated metal oxides are commonly used molybdenum oxide and vanadium oxide. The proposed approach of synthesizing cesium intercalated metal oxides has interesting properties of room‐temperature, ambient atmosphere, water free and solution process, favoring the formation of metal oxides as carrier transport layers at different regions in multilayered devices and large scale fabrication of organic optoelectronics at low cost. Besides the wide range of controllable workfunction adjustment, band structures, and electrical properties are investigated in detail, to understand the effects of cesium intercalation on metal oxides. The device results show that, using the proposed cesium intercalation approach, each of the two investigated metal oxides can function as both ETL and HTL in organic solar cells and organic light emitting diodes with very good device performances. Consequently, with the interesting properties in film synthesis, the proposed cesium intercalated metal oxides can achieve continuously workfunction tuning over a large range and contribute to evolution of the simple route for fabricating high performance organic optoelectronic devices.
Inhibition of Angiogenesis by Antioxidant Micelles
Authors: Moriyama Masaki , Metzger Stéphanie , van der Vlies André J. , Uyama Hiroshi , Ehrbar Martin , Hasegawa Urara
Published: September 2014

Antioxidant micelles capable of scavenging reactive oxygen species (ROS) are prepared from poly(ethylene glycol)‐b‐poly(dopamine) block copolymers. The micelles inhibit tube formation of human umbilical vein endothelial cells (HUVECs) by scavenging endogenous ROS. Furthermore, the micelles inhibit angiogenesis in the chicken ex ovo chorioallantoic membrane assay. The results show that antioxidant micelles containing catechol moieties may be useful in anti‐angiogenic therapy to treat various diseases such as cancer.
Synthesis of 2‐Substituted Indoles through Visible Light‐Induced Photocatalytic Cyclizations of Styryl Azides
Authors: Xia Xu‐Dong , Xuan Jun , Wang Qiang , Lu Liang‐Qiu , Chen Jia‐Rong , Xiao Wen‐Jing
Published: September 2014

A visible light‐induced photocatalytic intramolecular cyclization of styryl azides has been developed in the presence of the ruthenium complex Ru(bpy)3Cl2 (0.5 mol%) as photocatalyst at room temperature. The present photocatalytic strategy features operational simplicity as well as high functional group tolerance, and provides a facile access to various 2‐substituted N‐free indoles in good to excellent yields. Importantly, the present process can employ sunlight as the light source to afford the corresponding products without loss of reaction efficiency.

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Carbon Nitride‐Catalyzed Photoredox Sakurai Reactions and Allylborations
Authors: Möhlmann Lennart , Blechert Siegfried
Published: September 2014

Within the last couple of years, the photocatalytic, oxidative CC coupling has grown to a well‐established methodology, especially for the modification of aryl‐substituted tetrahydroisoquinoline derivatives. However, until now, this reaction is mainly restricted to the usage of strong nucleophiles like nitroalkanes, cyanides, enamines, phosphonates and malonates. Within this publication we present an extension of such a method towards the application of weaker nucleophiles, namely allylstannanes, allylsilanes and allylboranes. Therefore, a very simple protocol was invented, using heterogeneous mesoporous graphitic carbon nitride (mpg‐C3N4) as catalyst and air as oxidizing agent, leading to high yields for a broad range of substrates.

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Tetraphenylporphyrin‐Catalyzed Tandem Photooxygenation of Polyenes and 1,4‐Dienes: Multiple and Diverse Oxyfunctionalizations
Authors: Griesbeck Axel G. , de Kiff Alan , Kleczka Margarethe
Published: September 2014

Tandem singlet oxygen reactions photocatalyzed by meso‐tetraphenylporphyrin were performed with substrates designed for primary α‐gem‐selectivity or high vinylogous gem‐selectivity. The 1,3,5‐triene ester 1 was designed as a model compound for the natural compound crocin and resulted in a highly regioselective singlet oxygen ene reaction with ε‐hydrogen activation (93:7 ene vs. [4+2] cycloaddition). The initially formed hydroperoxide 2a adds another singlet oxygen molecule in a slower reaction step to furnish the endoperoxide 3a. From the hydroperoxide stage, oxygen transfer gives the epoxide 4, reduction leads to the allylic alcohol 2b and subsequent photooxygenation (to 3b) followed by reduction results in the furan derivative 5. The allylic alcohol could also be reacted with other dienophiles as shown for the PTAD adduct 6. From the 1,4‐diene 7, a gem‐regioselective singlet oxygen ene reaction generates a mixture of the hydroperoxides 8a and 9a. Product 8a adds another singlet oxygen molecule to give the endoperoxide 10a. Catalyst activity was demonstrated by analysis of the changes in the electronic absorption properties.

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Dual Photoredox and Gold Catalysis: Intermolecular Multicomponent Oxyarylation of Alkenes
Authors: Hopkinson Matthew N. , Sahoo Basudev , Glorius Frank
Published: September 2014

Intermolecular three‐component oxyarylation reactions of simple alkenes have been developed using a dual gold and photoredox catalytic system. Inexpensive organic dyes could be employed as the photocatalyst using aryldiazonium salts, while the combination of gold and iridium catalysts allowed for diaryliodonium compounds to be employed as the source of the arene coupling partner. In both cases, α‐arylated ether products were generated under remarkably mild conditions using readily accessible visible light sources.

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A Cascade Cross‐Coupling and in Situ Hydrogenation Reaction by Visible Light Catalysis
Authors: Zhong Jian‐Ji , Wu Cheng‐Juan , Meng Qing‐Yuan , Gao Xue‐Wang , Lei Tao , Tung Chen‐Ho , Wu Li‐Zhu
Published: September 2014

An elegant cascade cross‐coupling and in situ hydrogenation reaction has been established by visible light catalysis. Combining cheap and earth‐abundant eosin Y as a photosensitizer and the cobalt chloride complex, Co(dmgH)2Cl2 (dmgH=dimethylglyoximate), as a catalyst, the desired oxidative cross‐coupling products and reductive hydrogenation products could be achieved in good to excellent yields without use of any external oxidants and reductants under visible light irradiation.

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Visible Light Photocatalytic Reduction of O‐Thiocarbamates: Development of a Tin‐Free Barton–McCombie Deoxygenation Reaction
Authors: Chenneberg Ludwig , Baralle Alexandre , Daniel Marion , Fensterbank Louis , Goddard Jean‐Philippe , Ollivier Cyril
Published: September 2014

The Barton–McCombie deoxygenation is one of the most important transformations in the toolbox of organic chemists which has been the subject of a number of methodological developments. In this study, we report a photocatalyzed redox deoxygenation of secondary and tertiary alcohols from thiocarbamate precursors under visible light activation. The iridium complex Ir(ppy)3 proved to be the most efficient catalyst in the presence of Hünig’s base as sacrifial electron donor. A mechanistic investigation is presented based on fluorescence quenching experiments and cyclic voltammetry.

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Understanding Triplet Formation Pathways in Bulk Heterojunction Polymer:Fullerene Photovoltaic Devices
Authors: Tedlla Biniam Zerai , Zhu Feng , Cox Matthijs , Drijkoningen Jeroen , Manca Jean , Koopmans Bert , Goovaerts Etienne
Published: September 2014

Triplet exciton (TE) formation pathways are systematically investigated in prototype bulk heterojunction (BHJ) “super yellow” poly(p‐phenylene vinylene) (SY‐PPV) solar cell devices with varying fullerene compositions using complementary optoelectrical and electrically detected magnetic resonance (EDMR) spectroscopies. It is shown that EDMR spectroscopy allows the unambiguous demonstration of fullerene triplet production in BHJ polymer:fullerene solar cells. EDMR triplet detection under selective photoexcitation of each blend component and of the interfacial charge transfer (CT) state reveals that low lying fullerene TEs are produced by direct intersystem crossing from singlet excitons (SEs). The direct CT‐TE recombination pathway, although energetically feasible, is kinetically suppressed in these devices. However, high energy CT states in the CT manifold can contribute to the population of the fullerene triplet state via a direct CT‐SE conversion. This undesirable energetic alignment could be one of the causes for the severe reduction in photocurrent observed when the open‐circuit voltage of polymer:fullerene solar cells is pushed to 1.0 V or beyond.
Continuum approximation of large reaction mixtures in reactors with backmixing
Authors: Ho Teh C. , White Benjamin S.
Published: September 2014

The growing need to produce ultraclean fuels from hydrocarbon mixtures such as petroleum fractions and residues has put increasing pressure on refiners to achieve deep conversions. It is imperative to be able to predict the behavior of such mixtures at high conversions as functions of their properties and reactor type. To this end, treating the reaction mixture as a continuum greatly simplifies the analysis and modeling of the conversion process. However, the continuum approximation can become invalid at very high conversions. Previously, we examined the validity of the approximation for various reactions in plug flow reactors. The validity conditions for first‐order reaction mixtures in reactors with different mixing intensities are developed. In general, backmixing widens the range of validity. In certain cases, the continuum approximation is valid at arbitrarily high conversions. © 2014 American Institute of Chemical Engineers AIChE J, 61: 159–165, 2015
Pitheciids in fragmented habitats: Land cover change and its implications for conservation
Authors: Boyle Sarah A.
Published: September 2014

Pitheciids (Cacajao,Callicebus,Chiropotes, andPithecia) have experienced habitat loss and fragmentation across their geographic range in South America. Some populations living in habitat fragments live in smaller groups, travel shorter distances, and consume items that are not regularly found in the diets of populations living in continuous habitat; however, these patterns are not consistent across species. I used the IUCN Red List of Threatened Species to delineate the geographic range and conservation status of 43 pitheciid species. I calculated the amount of modified land cover within the range of each species, as well as the extent to which the remaining habitat exists in small fragments and the amount of forest lost from 2000 to 2012. Mean forest fragment size ranged from 12 to 12,027 ha, and mean forest loss from 2000 to 2012 ranged from 10.7% forChiropotesto 0.9% forPithecia. Critically Endangered and Endangered species represented 20.9% of the pitheciid species, and 46.5% of these species had population trends documented as decreasing. Total modified land cover was greatest forCallicebusspecies (18.0% of geographic range), followed byChiropotes(13.8%),Pithecia(4.4%), andCacajao(1.1%). Species of greater conservation concern had smaller geographic ranges, and a greater percentage of their range consisting of modified land cover than species of lower conservation concern. Species of greater conservation concern also had a greater percentage of forest lost from 2000 to 2012 and a smaller percentage of the remaining forest being protected. Most studies of pitheciids in fragments have concentrated on census data; the behavior of pitheciids in fragments has been examined for only 9 of the 43 species. Increased data on the responses of pitheciid species to forest loss and fragmentation are necessary in order to address pitheciid conservation, especially in areas undergoing severe habitat loss. Am. J. Primatol. 78:534–549, 2016. © 2014 Wiley Periodicals, Inc.
Molar crown inner structural organization in Javanese Homo erectus
Authors: Zanolli Clément
Published: September 2014

This contribution investigates the inner organizational pattern (tooth tissue proportions and enamel–dentine junction morphology) of seven Homo erectus permanent molar crowns from the late Lower‐early Middle Pleistocene Kabuh Formation of the Sangiran Dome (Central Java, Indonesia). The previous study of their external characteristics confirmed the degree of time‐related structural reduction occurred in Javanese H. erectus, and also revealed a combination of nonmetric features which are rare in the Lower and early Middle Pleistocene dental record, but more frequently found in recent humans. In accordance with their outer occlusal morphology, the specimens exhibit a set of derived internal features, such as thick to hyperthick enamel, an incomplete expression of the crest patterns at the enamel–dentine junction (EDJ) level, a sharp EDJ topography. As a whole, these features differ from those expressed in some penecontemporaneous specimens/samples representing African H. erectus/ergaster and H. heidelbergensis, as well as in Neanderthals, but occur in recent human populations. Further research in virtual dental paleoanthropology to be developed at macroregional scale would clarify the polarity and intensity of the intermittent exchanges between continental and insular Southeast Asia around the Lower to Middle Pleistocene boundary, as well as should shed light on the still poorly understood longitudinal evolutionary dynamics across continental Asia. Am J Phys Anthropol 156:148–157, 2015 © 2014 Wiley Periodicals, Inc.
Independent risk factors for a complicated hospital course in intensive care unit overdose patients
Authors: Tarui Takehiko , Yoshikawa Kei , Miyakuni Yasuhiko , Kaita Yasuhiko , Tamada Nao , Matsuda Taketo , Miyauchi Hiroshi , Yamada Kenji , Matsuda Takeaki , Yamaguchi Yoshihiro
Published: September 2014

Aim

The purpose of the present study was to identify risk factors associated with a complicated hospital course in overdose patients admitted to the intensive care unit.

Methods

A total of 335 overdose patients were retrospectively studied in the surgical and medical intensive care unit of an academic tertiary hospital. Factors possibly associated with a complicated hospital course were evaluated. Complicated hospital course was defined as the occurrence of pneumonia, rhabdomyolysis, decubitus ulcer, nerve palsy, prolonged intubation, prolonged hospitalization, or death.

Results

Of the 335 overdose patients, 93 (27.8%) had a complicated hospital course. Complicated hospital course was found to be associated with a high number of ingested pills (median, 135 [interquartile range, 78–240] versus 84 [53–134] tablets, P < 0.0001), low Glasgow Coma Scale score on admission (7 [3–11] versus 13 [8–15], P < 0.0001), and a high serum lactate level on admission (1.8 [1.0–3.0] versus 1.4 [0.9–2.0] mg/dL, P < 0.01) on univariate analysis of these factors in patients with and without a complicated hospital course. The independent risk factors for a complicated hospital course identified on multivariate analysis were a high number of ingested pills (≥100 tablets), low admission Glasgow Coma Scale score (<9), and high serum lactate on admission (≥2.0 mg/dL). The probability of a complicated hospital course for patients with 0, 1, 2, or all 3 independent risk factors were 7%, 22%, 40%, and 81%, respectively.

Conclusion

The total number of ingested pills, admission Glasgow Coma Scale score, and serum lactate level on admission are predictive of a complicated hospital course in overdose patients admitted to the intensive care unit.
Nickel(II)‐Catalyzed Asymmetric Propargyl and Allyl Claisen Rearrangements to Allenyl‐ and Allyl‐Substituted β‐Ketoesters
Authors: Liu Yangbin , Hu Haipeng , Zheng Haifeng , Xia Yong , Liu Xiaohua , Lin Lili , Feng Xiaoming
Published: September 2014

Highly efficient catalytic asymmetric Claisen rearrangements of O‐propargyl β‐ketoesters and O‐allyl β‐ketoesters have been accomplished under mild reaction conditions. In the presence of the chiral N,N′‐dioxide/NiII complex, a wide range of allenyl/allyl‐substituted all‐carbon quaternary β‐ketoesters was obtained in generally good yield (up to 99 %) and high diastereoselectivity (up to 99:1 d.r.) with excellent enantioselectivity (up to 99 % ee).
Control of Silver(I)–Dialkyl Chalcogenide Coordination by a Synthetic Cavity
Authors: Kohyama Yuh , Murase Takashi , Fujita Makoto
Published: September 2014

The discrete cavity of a self‐assembled palladium–tris(4‐pyridyl)triazine cage dictates the ratio of metal, ligand, and a non‐coordinative molecule in the formation of silver(I)–dialkyl chalcogenide (Et, nBu; S, Se) complexes and defines their coordination arrangement.
Bacterial Reaction Centers Purified with Styrene Maleic Acid Copolymer Retain Native Membrane Functional Properties and Display Enhanced Stability
Authors: Swainsbury David J. K. , Scheidelaar Stefan , van Grondelle Rienk , Killian J. Antoinette , Jones Michael R.
Published: September 2014

Integral membrane proteins often present daunting challenges for biophysical characterization, a fundamental issue being how to select a surfactant that will optimally preserve the individual structure and functional properties of a given membrane protein. Bacterial reaction centers offer a rare opportunity to compare the properties of an integral membrane protein in different artificial lipid/surfactant environments with those in the native bilayer. Here, we demonstrate that reaction centers purified using a styrene maleic acid copolymer remain associated with a complement of native lipids and do not display the modified functional properties that typically result from detergent solubilization. Direct comparisons show that reaction centers are more stable in this copolymer/lipid environment than in a detergent micelle or even in the native membrane, suggesting a promising new route to exploitation of such photovoltaic integral membrane proteins in device applications.
Reverse Spin‐Crossover and High‐Pressure Kinetics of the Heme Iron Center Relevant for the Operation of Heme Proteins under Deep‐Sea Conditions
Authors: Troeppner Oliver , Lippert Rainer , Shubina Tatyana E. , Zahl Achim , Jux Norbert , Ivanović‐Burmazović Ivana
Published: September 2014

By design of a heme model complex with a binding pocket of appropriate size and flexibility, and by elucidating its kinetics and thermodynamics under elevated pressures, some of the pressure effects are demonstrated relevant for operation of heme‐proteins under deep‐sea conditions. Opposite from classical paradigms of the spin‐crossover and reaction kinetics, a pressure increase can cause deceleration of the small‐molecule binding to the vacant coordination site of the heme‐center in a confined space and stabilize a high‐spin state of its Fe center. This reverse high‐pressure behavior can be achieved only if the volume changes related to the conformational transformation of the cavity can offset the volume changes caused by the substrate binding. It is speculated that based on these criteria nature could make a selection of structures of heme pockets that assist in reducing metabolic activity and enzymatic side reactions under extreme pressure conditions.
Palladium(0)‐Catalyzed Cross‐Coupling of 1,1‐Diboronates with Vinyl Bromides and 1,1‐Dibromoalkenes
Authors: Li Huan , Zhang Zhikun , Shangguan Xianghang , Huang Shan , Chen Jun , Zhang Yan , Wang Jianbo
Published: September 2014

Palladium‐catalyzed cross‐coupling reactions of 1,1‐diboronates with vinyl bromides and dibromoalkenes were found to afford 1,4‐dienes and allenes, respectively. These reactions utilize the high reactivities of both 1,1‐diboronates and allylboron intermediates generated in the initial coupling.
Supramolecular Transcription of Guanosine Monophosphate into Mesostructured Silica
Authors: Bueno‐Alejo Carlos J. , Villaescusa Luis A. , Garcia‐Bennett Alfonso E.
Published: September 2014

There is large interest in replicating biological supramolecular structures in inorganic materials that are capable of mimicking biological properties. The use of 5‐guanosine monophosphate in the presence of Na+ and K+ ions as a supramolecular template for the synthesis of well‐ordered mesostructured materials is reported here. Mesostructured particles with the confined template exhibit high structural order at both meso‐ and atomic scales, with a lower structural symmetry in the columnar mesophase. Although a chiral space group can not be deduced from X‐ray diffraction, analysis by electron microscopy and circular dichroism confirms a chiral stacking arrangement along the c‐axis. Guanosine monophosphate based mesophases thus illustrate the possibility for specific molecular imprinting of mesoporous materials by genetic material and the potential for higher definition in molecular recognition.
Translating Bacterial Detection by DNAzymes into a Litmus Test
Authors: Tram Kha , Kanda Pushpinder , Salena Bruno J. , Huan Shuangyan , Li Yingfu
Published: September 2014

Microbial pathogens pose serious threats to public health and safety, and results in millions of illnesses and deaths as well as huge economic losses annually. Laborious and expensive pathogen tests often represent a significant hindrance to implementing effective front‐line preventative care, particularly in resource‐limited regions. Thus, there is a significant need to develop low‐cost and easy‐to‐use methods for pathogen detection. Herein, we present a simple and inexpensive litmus test for bacterial detection. The method takes advantage of a bacteria‐specific RNA‐cleaving DNAzyme probe as the molecular recognition element and the ability of urease to hydrolyze urea and elevate the pH value of the test solution. By coupling urease to the DNAzyme on magnetic beads, the detection of bacteria is translated into a pH increase, which can be readily detected using a litmus dye or pH paper. The simplicity, low cost, and broad adaptability make this litmus test attractive for field applications, particularly in the developing world.
Carbon Nanofibers Decorated with Molybdenum Disulfide Nanosheets: Synergistic Lithium Storage and Enhanced Electrochemical Performance
Authors: Zhou Fei , Xin Sen , Liang Hai‐Wei , Song Lu‐Ting , Yu Shu‐Hong
Published: September 2014

Traditional lithium‐ion batteries that are based on layered Li intercalation electrode materials are limited by the intrinsically low theoretical capacities of both electrodes and cannot meet the increasing demand for energy. A facile route for the synthesis of a new type of composite nanofibers, namely carbon nanofibers decorated with molybdenum disulfide sheets (CNFs@MoS2), is now reported. A synergistic effect was observed for the two‐component anode, triggering new electrochemical processes for lithium storage, with a persistent oxidation from Mo (or MoS2) to MoS3 in the repeated charge processes, leading to an ascending capacity upon cycling. The composite exhibits unprecedented electrochemical behavior with high specific capacity, good cycling stability, and superior high‐rate capability, suggesting its potential application in high‐energy lithium‐ion batteries.
One‐Step Multicomponent Self‐Assembly of a First‐Generation Sierpiński Triangle: From Fractal Design to Chemical Reality
Authors: Sarkar Rajarshi , Guo Kai , Moorefield Charles N. , Saunders Mary Jane , Wesdemiotis Chrys , Newkome George R.
Published: September 2014

A novel terpyridine‐based architecture that mimics a first‐generation Sierpiński triangle has been synthesized by multicomponent assembly and features tpyCdIItpy connectivity (tpy=terpyridine). The key terpyridine ligands were synthesized by the Suzuki cross‐coupling reaction. Mixing two different terpyridine‐based ligands and CdII in a precise stoichiometric ratio (1:1:3) produced the desired fractal architecture in near‐quantitative yield. Characterization was accomplished by NMR spectroscopy, mass spectrometry, and transmission electron microscopy.
Herkunft und Verbleib von Elektronen und Protonen bei der Bildung des intermetalloiden Clusters [Sm@Ga3−xH3−2xBi10+x]3− (x=0, 1)
Authors: Weinert Bastian , Müller Fabian , Harms Klaus , Clérac Rodolphe , Dehnen Stefanie
Published: September 2014

Die Reaktion von [GaBi3]2− mit [Sm(C5Me4H)3] führte zur Bildung des ersten protonierten ternären intermetalloiden Clusters [Sm@Ga3−xH3−2xBi10+x]3− (1; x=0,1). Die Existenz von Ga‐H‐Bindungen und der Transfer von Elektronen und Protonen während der Bildung von 1 wurde durch Kombination verschiedener experimenteller und quantenchemischer Methoden beleuchtet, was auch die Rolle des Lösungsmittels 1,2‐Diaminoethan als Brønsted‐Säure unterstrich. Als organisches Nebenprodukt wurde das bisher nicht bekannte Octamethylfulven (2) erhalten, das durch eine C‐C‐Kupplung aus (C5Me4H)− hervorging.
Switchable Amplification of Vibrational Circular Dichroism as a Probe of Local Chiral Structure
Authors: Domingos Sérgio R. , Sanders Hans J. , Hartl František , Buma Wybren J. , Woutersen Sander
Published: September 2014

A new method to detect the vibrational circular dichroism (VCD) of a localized part of a chiral molecular system is reported. A local VCD amplifier was implemented, and the distance dependence of the amplification was investigated in a series of peptides. The results indicate a characteristic distance of 2.0±0.3 bonds, which suggests that the amplification is a localized phenomenon. The amplifier can be covalently coupled to a specific part of a molecule, and can be switched ON and OFF electrochemically. By subtracting the VCD spectra obtained when the amplifier is in the ON and OFF states, the VCD of the local environment of the amplifier can be separated from the total VCD spectrum. Switchable local VCD amplification thus makes it possible to “zoom in” on a specific part of a chiral molecule.
Chemical Probes for the Functionalization of Polyketide Intermediates
Authors: Riva Elena , Wilkening Ina , Gazzola Silvia , Li W. M. Ariel , Smith Luke , Leadlay Peter F. , Tosin Manuela
Published: September 2014

A library of functionalized chemical probes capable of reacting with ketosynthase‐bound biosynthetic intermediates was prepared and utilized to explore in vivo polyketide diversification. Fermentation of ACP mutants of S. lasaliensis in the presence of the probes generated a range of unnatural polyketide derivatives, including novel putative lasalocid A derivatives characterized by variable aryl ketone moieties and linear polyketide chains (bearing alkyne/azide handles and fluorine) flanking the polyether scaffold. By providing direct information on microorganism tolerance and enzyme processing of unnatural malonyl‐ACP analogues, as well as on the amenability of unnatural polyketides to further structural modifications, the chemical probes constitute invaluable tools for the development of novel mutasynthesis and synthetic biology.
Single‐Chain Magnetic Behavior in a Hetero‐Tri‐Spin Complex Mediated by Supramolecular Interactions with TCNQF.− Radicals
Authors: Wang Zhao‐Xi , Zhang Xuan , Zhang Yuan‐Zhu , Li Ming‐Xing , Zhao Hanhua , Andruh Marius , Dunbar Kim R.
Published: September 2014

The self‐assembly of organic TCNQF.− radicals (2‐fluoro‐7,7,8,8‐tetracyano‐p‐quinodimethane) and the anisotropic [Tb(valpn)Cu]3+ dinuclear cations produced a single‐chain magnet (SCM) involving stacking interactions of TCNQF.− radicals (H2valpn is the Schiff base from the condensation of o‐vanillin with 1,3‐diaminopropane). Static and dynamic magnetic characterizations reveal that the effective energy barrier for the reversal of the magnetization in this hetero‐tri‐spin SCM is significantly larger than the barrier of the isolated single‐molecule magnet based on the {TbCu} dinuclear core.
Solvent Effects in Acid‐Catalyzed Biomass Conversion Reactions
Authors: Mellmer Max A. , Sener Canan , Gallo Jean Marcel R. , Luterbacher Jeremy S. , Alonso David Martin , Dumesic James A.
Published: September 2014

Reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid‐catalyzed conversion of xylose into furfural. A solvent of particular importance is γ‐valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2‐propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Brønsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabilization of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Brønsted acid catalysts, such as H‐mordenite and H‐beta.
Hexagonal Transition‐Metal Chalcogenide Nanoflakes with Pronounced Lateral Quantum Confinement
Authors: Miró Pere , Han Jae Hyo , Cheon Jinwoo , Heine Thomas
Published: September 2014

Transition‐metal chalcogenide (TMC) nanoflakes of composition MX2(where M=Ti, Zr and Hf; X=S and Se) crystallize preferentially in equilateral hexagons and exhibit a pronounced lateral quantum confinement. The hexagonal shape of octahedral (1T) TMC nanoflakes is the result of charge localization at the edges/vertices and the resulting Coulomb repulsion. Independent of their size, all nanoflakes have the MnX2n−2stoichiometry and thus an unoxidized metal center which results in dopant states. These states become relevant for small nanoflakes and lead to metallic character, but for larger nanoflakes (>6 nm) the 2D monolayer properties dominate. Finally, coordination of Lewis bases at the nanoflake edges has no significant effect on the electronic structure of these species confirming the viability of colloidal synthetic approaches.
Cu–Al Spinel Oxide as an Efficient Catalyst for Methanol Steam Reforming
Authors: Xi Hongjuan , Hou Xiaoning , Liu Yajie , Qing Shaojun , Gao Zhixian
Published: September 2014

Cu–Al spinel oxide, which contains a small portion of the CuO phase, has been successfully used in methanol steam reforming (MSR) without prereduction. The omission of prereduction not only avoids the copper sintering prior to the catalytic reaction, but also slows down the copper‐sintering rate in MSR. During this process, the CuO phase can initiate MSR at a lower temperature, and CuAl2O4 releases active copper gradually. The catalyst CA2.5‐900, calcined at 900 °C with n(Al)/n(Cu)=2.5, has a higher CuAl2O4 content, higher BET surface area, and smaller CuAl2O4 crystal size. Its activity first increases and then decreases during MSR. Furthermore, both fresh and regenerated CA2.5‐900 showed better catalytic performance than the commercial Cu–Zn–Al catalyst.
Cleavage and Formation of Molecular Dinitrogen in a Single System Assisted by Molybdenum Complexes Bearing Ferrocenyldiphosphine
Authors: Miyazaki Takamasa , Tanaka Hiromasa , Tanabe Yoshiaki , Yuki Masahiro , Nakajima Kazunari , Yoshizawa Kazunari , Nishibayashi Yoshiaki
Published: September 2014

The NN bond of molecular dinitrogen bridging two molybdenum atoms in the pentamethylcyclopentadienyl molybdenum complexes that bear ferrocenyldiphosphine as an auxiliary ligand is homolytically cleaved under visible light irradiation at room temperature to afford two molar molybdenum nitride complexes. Conversely, the bridging molecular dinitrogen is reformed by the oxidation of the molybdenum nitride complex at room temperature. This result provides a successful example of the cleavage and formation of molecular dinitrogen induced by a pair of two different external stimuli using a single system assisted by molybdenum complexes bearing ferrocenyldiphosphine under ambient conditions.
Two‐Component Supramolecular Gels Derived from Amphiphilic Shape‐Persistent Cyclo[6]aramides for Specific Recognition of Native Arginine
Authors: He Youzhou , Xu Min , Gao Rongzhao , Li Xiaowei , Li Fengxue , Wu Xuedan , Xu Dingguo , Zeng Huaqiang , Yuan Lihua
Published: September 2014

A unique supramolecular two‐component gelation system was constructed from amphiphilic shape‐persistent cyclo[6]aramides and diethylammonium chloride (or triethylammonium chloride). This system has the ability to discriminate native arginine from 19 other amino acids in a specific fashion. Cyclo[6]aramides show preferential binding for the guanidinium residue over ammonium groups. This specificity was confirmed by both experimental results and theoretical simulations. These results demonstrated a new modular displacement strategy, exploring the use of species‐binding hydrogen‐bonded macrocyclic foldamers for the construction of two‐component gelation systems for selective recognition of native amino acids by competitive host–guest interactions. This strategy may be amenable to developing a variety of functional two‐component gelators for specific recognition of various targeted organic molecular species.
Enzymatic Polyketide Chain Branching To Give Substituted Lactone, Lactam, and Glutarimide Heterocycles
Authors: Heine Daniel , Bretschneider Tom , Sundaram Srividhya , Hertweck Christian
Published: September 2014

Polyketides typically result from head‐to‐tail condensation of acyl thioesters to produce highly functionalized linear chains. The biosynthesis of the phytotoxin rhizoxin, however, involves a polyketide synthase (PKS) module that introduces a δ‐lactone chain branch through Michael addition of a malonyl extender to an α,β‐unsaturated intermediate unit. To evaluate the scope of the branching module, polyketide mimics were synthesized and their biotransformation by the reconstituted PKS module from the Rhizopus symbiont Burkholderia rhizoxinica was monitored in vitro. The impact of the type and configuration of the δ‐substituents was probed and it was found that amino‐substituted surrogates yield the corresponding lactams. A carboxamide analogue was transformed into a glutarimide unit, which can be found in many natural products. Our findings illuminate the biosynthesis of glutarimide‐bearing polyketides and also demonstrate the utility of this branching module for synthetic biology.
Luminescence, Stability, and Proton Response of an Open‐Shell (3,5‐Dichloro‐4‐pyridyl)bis(2,4,6‐trichlorophenyl)methyl Radical
Authors: Hattori Yohei , Kusamoto Tetsuro , Nishihara Hiroshi
Published: September 2014

A luminescent open‐shell organic radical with high chemical stability was synthesized. (3,5‐Dichloro‐4‐pyridyl)bis(2,4,6‐trichlorophenyl)methyl radical (PyBTM) was photoluminescent under various conditions. Fluorescence quantum yields of 0.03, 0.26, and 0.81 (the highest value reported for a stable organic radical) were obtained in chloroform, in poly(methyl methacrylate) film at room temperature, and in an EPA matrix (diethyl ether:isopentane:ethanol) at 77 K, respectively. The photostability of PyBTM is up to 115 times higher than that of the tris(2,4,6‐trichlorophenyl)methyl radical, a previously reported luminescent radical. The pyridine moiety of PyBTM acts as a proton coordination site, thereby allowing for control of the electronic and optical properties of the radical by protonation and deprotonation.
Simultaneous Detection of Single Attoliter Droplet Collisions by Electrochemical and Electrogenerated Chemiluminescent Responses
Authors: Dick Jeffrey E. , Renault Christophe , Kim Byung‐Kwon , Bard Allen J.
Published: September 2014

We provide evidence of single attoliter oil droplet collisions at the surface of an ultra‐microelectrode (UME) by the observation of simultaneous electrochemical current transients (i–t curves) and electrogenerated chemiluminescent (ECL) transients in an oil/water emulsion. An emulsion system based on droplets of toluene and tri‐n‐propylamine (2:1 v/v) emulsified with an ionic liquid and suspended in an aqueous continuous phase was formed by ultrasonification. When an ECL luminophore, such as rubrene, is added to the emulsion droplet, stochastic events can be tracked by observing both the current blips from oxidation at the electrode surface and the ECL blips from the follow‐up ECL reaction, which produces light. This report provides a means of studying fundamental aspects of electrochemistry using the attoliter oil droplet and offers complementary analytical techniques for analyzing discrete collision events, size distribution of emulsion systems, and individual droplet electroactivity.
A CXCR4‐Targeted Site‐Specific Antibody–Drug Conjugate
Authors: Kularatne Sumith A. , Deshmukh Vishal , Ma Jennifer , Tardif Virginie , Lim Reyna K. V. , Pugh Holly M. , Sun Ying , Manibusan Anthony , Sellers Aaron J. , Barnett Richard S. , Srinagesh Shailaja , Forsyth Jane S. , Hassenpflug Wolf , Tian Feng , Javahishvili Tsotne , Felding‐Habermann Brunhilde , Lawson Brian R. , Kazane Stephanie A. , Schultz Peter G.
Published: September 2014

A chemically defined anti‐CXCR4–auristatin antibody–drug conjugate (ADC) was synthesized that selectively eliminates tumor cells overexpressing the CXCR4 receptor. The unnatural amino acid p‐acetylphenylalanine (pAcF) was site‐specifically incorporated into an anti‐CXCR4 immunoglobulin G (IgG) and conjugated to an auristatin through a stable, non‐cleavable oxime linkage to afford a chemically homogeneous ADC. The full‐length anti‐CXCR4 ADC was selectively cytotoxic to CXCR4+ cancer cells in vitro (half maximal effective concentration (EC50)≈80–100 pM). Moreover, the anti‐CXCR4 ADC eliminated pulmonary lesions from human osteosarcoma cells in a lung‐seeding tumor model in mice. No significant overt toxicity was observed but there was a modest decrease in the bone‐marrow‐derived CXCR4+ cell population. Because CXCR4 is highly expressed in a majority of metastatic cancers, a CXCR4–auristatin ADC may be useful for the treatment of a variety of metastatic malignancies.
In vitro toxicity evaluation of hydrogel–carbon nanotubes composites on intestinal cells
Authors: Bellingeri Romina , Alustiza Fabrisio , Picco Natalia , Acevedo Diego , Molina Maria Alejandra , Rivero Rebeca , Grosso Carolina , Motta Carlos , Barbero Cesar , Vivas Adriana
Published: September 2014

Composite materials based on carbon nanotubes (CNT) and polymeric hydrogels have become the subject matter of major interest for use as carriers in drug delivery research. The aim of this study was to evaluate the in vitro cytotoxicity of the hydrogel–carbon nanotube–chitosan (hydrogel–CNT–CH) composites on intestinal cells. Oxidized CNT were wrapped with chitosan (CH), Fourier transform infrared (FT‐IR) analysis suggest that oxidized CNT interact with CH. Transmission electron microscopy (TEM) images show a CH layer lying around CNT. Chitosan wrapped CNT were incorporated to poly (acrylamide‐co‐acrylic acid) hydrogels. Swelling behavior in buffers at different pH were evaluated and revealed a significantly lower swelling when it is exposed to a acid buffer solution (pH 2.2). Mechanical properties were evaluated by measurements of elasticity and the material with CNT showed better mechanical properties. The incorporation and liberation of Egg Yolk Immunoglobulin from hydrogel–CNT–CH were also assessed and it revealed an improved performance. To evaluate the effect of these nanocomposites on cellular redox balance, intestinal cells were exposed to hydrogel–CNT–CH composites and antioxidant enzymes were assessed. Cytotoxicity and apoptosis were also evaluated. Hydrogel–CNT–CH composites induce no oxidative stress and there were no evidence of cytotoxicity or cell death. These preliminary findings suggest that hydrogel–CNT–CH composites show improved properties and good biocompatibility in vitro making these biomaterials promising systems for drug delivery purposes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41370.
Effect of montmorillonite on the rheological properties of dually crosslinked guar gum‐based hydrogels
Authors: Branca Caterina , Crupi Cristina , D'Angelo Giovanna , Khouzami Khaoula , Rifici Simona , Visco Annamaria , Wanderlingh Ulderico
Published: September 2014

One strategy to create chemical and physical cross‐links simultaneously is to introduce into the chemical network hydrogen bonding with clay nanofillers. Understanding the relaxation mechanisms of these systems is crucially important and has drawn the extensive interest of many scientists. In this work, the influence of different amounts of montmorillonite on the structural and rheological properties of guar gum hydrogels was investigated. Depending on the clay content, different nanostructures were identified by X‐ray diffraction (XRD) and their effect on the rheological properties of the dual hydrogels was studied. From stress and frequency sweep tests it emerged that all the samples exhibit a weak gel behavior and showed a maximum for G″ that can be ascribed to the breaking and reforming of transient physical crosslinks. This relaxation mode is more pronounced for the hydrogel for which a minimum in the swelling degree was observed. On the basis of these results, a model structure was proposed according to which the clay sheets act as effective multifunctional cross‐linkers. The more homogeneously dispersed are the clay platelets, the higher is the density of physical crosslinks. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41373.
Compatibility of cassava starch films as nitric oxide carrier for potential medical device
Authors: de Fazio Aguiar Helena , Júnior Antonio Carlos Roveda , de Jesus Piva Renan , Onoda Kevin Akira , Miyakawa Ayumi Aurea , Krieger Jose Eduardo , Franco Douglas Wagner , Tadini Carmen Cecilia
Published: September 2014

Films prepared with bioabsorbable materials (cassava starch, glycerol, and carboxymethyl cellulose (CMC)) can be used as an external support in the myocardial revascularization surgery, releasing nitric oxide (NO) during the tissue regeneration. In the present study, these materials submitted to in vitro degradation tests under physiological conditions, presented the reduction of 38% of weight loss by the modification of native starch using sodium trimetaphosphate (STMP) (15 g/100g of starch). The CMC addition of 10 g/100g of cassava starch increased 119% of the tensile strength of the films in comparison with films prepared without CMC. It was verified that the ruthenium complex trans‐[Ru(NH3)4(isn)(NO)](BF4)3 incorporated in the starch based films behave similarly as in aqueous solution, releasing NO by photochemical reaction. Macrophage cells were detected in in vivo degradation tests in rats around the implant after 1 and 7 days, and complete biodegradation was observed after 30 days. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41382.