bluuebunny/crossref_metadata_2025 huggingface dataset:
Inductive‐dynamic magnetosphere‐ionosphere coupling via MHD waves
Authors: Tu Jiannan , Song Paul , Vasyliūnas Vytenis M.
Published: January 2014

In the present study, we investigate magnetosphere‐ionosphere/thermosphere (M‐IT) coupling via MHD waves by numerically solving time‐dependent continuity, momentum, and energy equations for ions and neutrals, together with Maxwell's equations (Ampère's and Faraday's laws) and with photochemistry included. This inductive‐dynamic approach we use is fundamentally different from those in previous magnetosphere‐ionosphere (M‐I) coupling models: all MHD wave modes are retained, and energy and momentum exchange between waves and plasma are incorporated into the governing equations, allowing a self‐consistent examination of dynamic M‐I coupling. Simulations, using an implicit numerical scheme, of the 1‐D ionosphere/thermosphere system responding to an imposed convection velocity at the top boundary are presented to show how magnetosphere and ionosphere are coupled through Alfvén waves during the transient stage when the IT system changes from one quasi steady state to another. Wave reflection from the low‐altitude ionosphere plays an essential role, causing overshoots and oscillations of ionospheric perturbations, and the dynamical Hall effect is an inherent aspect of the M‐I coupling. The simulations demonstrate that the ionosphere/thermosphere responds to magnetospheric driving forces as a damped oscillator.
Tests of fixity of the Indo‐Atlantic hot spots relative to Pacific hot spots
Authors: Koivisto Emilia A. , Andrews David L. , Gordon Richard G.
Published: January 2014

Rates of inter‐hot spot motion have been debated for decades. Herein we present updated predictions for the tracks of the Tristan da Cunha, Réunion, and Iceland hot spots assuming them to be fixed relative to Pacific hot spots. Uncertainties in Pacific hot spot rotations, which include uncertainties in the current locations of hot spots of 100–200 km, are combined with uncertainties in relative plate motions accumulated through the plate circuit to obtain the final uncertainty in the predicted positions (including uncertainties of 150–200 km in the current locations of the Indo‐Atlantic hot spots). Improvements to reconstruction methods, to relative plate reconstructions, to age dates along the tracks, and to the geomagnetic reversal timescale lead to significant changes from prior results. When compared with the observed tracks, the predicted tracks indicate nominal rates of motion of only 2–6 mm a−1 of these Indo‐Atlantic hot spots relative to Pacific hot spots over the past 48 Ma. Within the uncertainties, the rates range from no motion to rates as high as 8–13 mm a−1. For reconstructions prior to 48 Ma B.P., however, the apparent rates of inter‐hot spot motion are much larger, 46–55 ± 20 mm a−1, if the motion occurred entirely between 68 Ma B.P. and 48 Ma B.P. Either hot spots moved rapidly before 48 Ma B.P., and slowed drastically at ≈ 48 Ma B.P., or global plate circuits through Antarctica become less reliable as one goes increasingly further into the past. Most paleomagnetic data favor the latter explanation.
The impact of Rayleigh number on assessing the significance of supercontinent insulation
Authors: Heron Philip J. , Lowman Julian P.
Published: January 2014

Several processes unfold during the supercontinent cycle, more than one of which might result in an elevation in subcontinental mantle temperatures, thus multiple interpretations of the concept of continental insulation exist. Although a consensus seems to have formed that subcontinental mantle upwellings appear below large continents extensively ringed by subduction zones, there are differing views on what role continental insulation plays in the production of elevated mantle temperatures. Here we investigate how the heating mode of the mantle can change the influence of the “thermal blanket” effect. We present 2‒D and 3‒D Cartesian geometry mantle convection simulations with thermally and mechanically distinct oceanic and continental plates. The evolution of mantle thermal structure is examined after continental accretion at subduction zones (e.g., the formation of Pangea) for a variety of different mantle‒heating modes. Our results show that in low‒Rayleigh number models the impact of the role of continental insulation on subcontinental temperatures increases, when compared to models with higher convective vigor. Broad, hot upper mantle features generated in low‒Rayleigh number models (due, in part, to the thermal blanket effect) are absent at higher Rayleigh numbers. We find that subcontinental heating in a high‒Rayleigh number flow occurs almost entirely as a consequence of the influence of subduction initiation at the continental margin, rather than the influence of continental insulation. In our models featuring Earth‒like convective vigor, we find that it is difficult to obtain subcontinental temperatures in significant excess of suboceanic temperatures over timescales relevant to supercontinent aggregation.
Fresh shallow valleys in the Martian midlatitudes as features formed by meltwater flow beneath ice
Authors: Hobley Daniel E. J. , Howard Alan D. , Moore Jeffrey M.
Published: January 2014

Significant numbers of valleys have been identified in the Martian midlatitudes (30–60°N/S), spatially associated with extant or recent ice accumulations. Many of these valleys date to the Amazonian, but their formation during these cold, dry epochs is problematic. In this study, we look in detail at the form, distribution, and quantitative geomorphology of two suites of these valleys and their associated landforms in order to better constrain the processes of their formation. Since the valleys themselves are so young and thus well preserved, uniquely, we can constrain valley widths and courses and link these to the topography from the Mars Orbiter Laser Altimeter and High‐Resolution Stereo Camera data. We show that the valleys are both qualitatively and quantitatively very similar, despite their being >5000 km apart in different hemispheres and around 7 km apart in elevation. Buffered crater counting indicates that the ages of these networks are statistically identical, probably forming during the Late Amazonian, ~100 Ma. In both localities, at least tens of valleys cross local drainage divides, apparently flowing uphill. We interpret these uphill reaches to be characteristic of flow occurring beneath a now absent, relatively thin (order 101–102 m), regionally extensive ice cover. Ridges and mounds occasionally found at the foot of these valley systems are analogous to eskers and aufeis‐like refreezing features. On the basis of their interaction with these aufeis‐like mounds, we suggest that this suite of landforms may have formed in a single, short episode (perhaps order of days), probably forced by global climate change.
Secondary electron emission from Martian soil simulant
Authors: Pavlů J. , Beránek M. , Vaverka J. , Šafránková J. , Němeček Z. , Richterová I.
Published: January 2014

In the recent years, growing interest in dust charging physics is connected with several lander missions running on or planned to the Moon, Mars, and Mercury for a near future. In support of these missions, laboratory simulations are a potential tool to optimize in situ exploration and measurements. In the paper, we have investigated electrical properties of a Martian soil simulant prepared at the Johnson Space Center under name JSC Mars‐1 using the dust charging experiment when a single dust grain is trapped in a vacuum chamber and its secondary electron emission is studied. The exposure of the grain to the electron beam revealed that the grain surface potential is low and generally determined by a mean atomic number of the grain material at a low‐energy range (<1 keV), whereas it can reach a limit of the field ion emission being irradiated by more energetic electrons. A comparison of model and experimental results reveals an influence of the grain shape and size predominantly in the range of higher (>2 keV) electron energies. We discuss possible implications of the secondary electron emission for the presence of lightnings on Mars.
Variable deceleration of Whillans Ice Stream, West Antarctica
Authors: Beem L. H. , Tulaczyk S. M. , King M. A. , Bougamont M. , Fricker H. A. , Christoffersen P.
Published: January 2014

The Whillans Ice Stream Ice Plain (WIP) has been slowing since at least 1963. Prior constraints on this slowdown were consistent with a constant long‐term deceleration rate. New observations of ice velocity from 11 continuous and 3 seasonal GPS sites indicate the deceleration rate varies through time including on interannual time scales. Between 2009 and 2012 WIP decelerated at a rate (6.1 to 10.9 ± 2 m/yr2) that was double the multidecadal average (3.0 to 5.6 ± 2 m/yr2). To identify the causes of slowdown, we used new and prior velocity estimates to constrain longitudinal and transverse force budget models as well as a higher‐order inverse model. All model results support the conclusion that the observed deceleration of WIP is caused by an increase in basal resistance to motion at a rate of 10 to 40 Pa/yr. Subglacial processes that may be responsible for strengthening the ice stream bed include basal freeze on, changes in subglacial hydrology, or increases in the area of resistant basal substrate through differential erosion. The observed variability in WIP deceleration rate suggests that dynamics in subglacial hydrology, plausibly driven by basal freeze on and/or activity of subglacial lakes, plays a key role in modulating basal resistance to ice motion in the region.
Gel–Liposome‐Mediated Co‐Delivery of Anticancer Membrane‐Associated Proteins and Small‐Molecule Drugs for Enhanced Therapeutic Efficacy
Authors: Jiang Tianyue , Mo Ran , Bellotti Adriano , Zhou Jianping , Gu Zhen
Published: January 2014

A programmed drug‐delivery system that can transport different anticancer therapeutics to their distinct targets holds vast promise for cancer treatment. Herein, a core–shell‐based “nanodepot” consisting of a liposomal core and a crosslinked‐gel shell (designated Gelipo) is developed for the sequential and site‐specific delivery (SSSD) of tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) and doxorubicin (Dox). As a small‐molecule drug intercalating the nuclear DNA, Dox is loaded in the aqueous core of the liposome, while TRAIL, acting on the death receptor (DR) on the plasma membrane, is encapsulated in the outer shell made of crosslinked hyaluronic acid (HA). The degradation of the HA shell by HAase that is concentrated in the tumor environment results in the rapid extracellular release of TRAIL and subsequent internalization of the liposomes. The parallel activity of TRAIL and Dox show synergistic anticancer efficacy. The half‐maximal inhibitory concentration (IC50) of TRAIL and Dox co‐loaded Gelipo (TRAIL/Dox‐Gelipo) toward human breast cancer (MDA‐MB‐231) cells is 83 ng mL–1 (Dox concentration), which presents a 5.9‐fold increase in the cytotoxicity compared to 569 ng mL–1 of Dox‐loaded Gelipo (Dox‐Gelipo). Moreover, with the programmed choreography, Gelipo significantly improves the inhibition of the tumor growth in the MDA‐MB‐231 xenograft tumor animal model.
Gold(I)‐Catalyzed Reactions of 1‐(ortho‐Alkynylaryl)ureas: Highly Selective Heterocyclization and Synthesis of Mixed N,O‐Acetals
Authors: Gimeno Ana , Cuenca Ana B. , Medio‐Simón Mercedes , Asensio Gregorio
Published: January 2014

Readily available 1‐(ortho‐ethynylaryl)urea derivatives undergo a selective gold/silver {[AuCl(IPr)]/AgSbF6} catalyzed N‐6‐exo‐dig or N‐5‐endo‐dig heterocyclization process in dimethylformamide (DMF) at 60 °C. Benzoxazine derivatives, i.e., the products of O‐6‐exo‐dig ring closure through the urea oxygen, could be observed under catalytic conditions only when the N‐3 basicity was substantially diminished, but were readily isolable in stoichiometric processes carried out at low temperature. The open chain amino O,O‐acetals and a series of new cyclic mixed N,O‐acetals containing the trifluoroethyl group were synthesized when the reactions were performed in ethanol or trifluoroethanol, respectively, as solvent. The procedure allows for an easy access to this versatile class of key intermediates in organic synthesis from simple starting materials. The effect of using either DMF or protic solvents on the course of the reactions is reported.

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Photochemical and acoustic interactions of biochar with CO2 and H2O: Applications in power generation and CO2 capture
Authors: Chen Wei‐Yin , Mattern Daniell L. , Okinedo Eneruvie , Senter James Corbett , Mattei Alec A. , Redwine Connor W.
Published: January 2014

A critical literature review suggests that carbonaceous compounds react with (CO2 +H2O) mixture through thermal, photochemical, and sonochemical/sonophysical routes. A biochar was selected for studying these effects at 60°C and 1 atm for its potential benefits on power generation and CO2 capture. All treatments remove sizable minerals (K, Na, and Si) detrimental in power generation, and introduce carbon (up to 16% of original carbon in biochar) into the biochar matrix. Most treatments show increased hydrogen (up to 24%). Treatments lead to notable increased heating value of biochar (up to 50%). Treated biochars show increase (up to 19 fold) in internal surface area. The ultrasound energy output is a fraction of the increased heating value. Thus, pretreatment is potentially attractive for increasing the energy efficiency in combustion and gasification. Moreover, better understandings of the salient reactions of these processes will be advantageous for the development of advanced adsorbents for CO2 capture. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1054–1065, 2014
Creation and evaluation of a single‐chain antibody tetramer that targets brain endothelial cells
Authors: Zhang Xiaobin , Wang Xin Xiang , Shusta Eric V.
Published: January 2014

Antibodies that target and internalize into blood‐brain barrier (BBB) endothelial cells offer promise as drug delivery agents. Previously, we identified a single‐chain antibody (scFvA) capable of binding to the BBB. In an attempt to improve the binding and internalization properties of scFvA, a biotinylation tag (Avitag) was fused to scFvA and the protein secreted by yeast. The scFvA‐Avitag could be biotinylated by yeast‐displayed BirA enzyme and biotinylated scFvA‐Avitag could be used to create scFv tetramers. Tetramerization of scFvA improved the internalization of scFvA into BBB endothelial cells, and biotinylated scFvA‐Avitag could also be used to target streptavidin‐coated quantum dots for BBB endothelial cell internalization. Perfusing the rat brain with scFvA‐tetramer confirmed that the antigen targeted by scFvA is distributed on the blood side of the BBB, suggesting the potential for downstream application of scFvA in brain‐targeted drug delivery. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1245–1252, 2014
Poly(ether imide) membranes modified with charged surface‐modifying macromolecule—Its performance characteristics as ultrafiltration membranes
Authors: Kanagaraj Palsamy , Neelakandan Sivasubramaniyan , Nagendran Alagumalai
Published: January 2014

Modification of poly (ether imide) (PEI) ultrafiltration (UF) membranes was attempted by blending charged surface modifying macromolecule (cSMM). Compared to the pure PEI membrane, blending of PEI with cSMM resulted in blend membranes with enhanced UF characteristics such as lower hydraulic resistance (Rm) and higher pure water flux (PWF) coupled with higher water content (WC). Among the various modified membranes, blend membranes with 5 wt % cSMM concentration exhibited higher PWF (60.38 L m−2 h−1), WC (73.6%), protein permeate flux (27.12 L m−2 h−1) and lower flux decline rate (Rfd) (55.1%), Rm (5.21 kPa/L m−2 h−1), bovine serum albumin (BSA) rejection (87.1%). Meanwhile, the fouling resistant ability was studied by flux recovery ratio (FRR) after water and alkali cleaning, irreversible and reversible fouling rate. Higher FRR after water cleaning (95.07%), FRR after alkali cleaning (97.1%), reversible fouling rate (50.14%) and lower irreversible fouling rate (5%) exhibited by 5 wt % cSMM membranes showed its better antifouling ability compared to pure PEI and other blend membranes because of its higher hydrophilic nature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40320.
New Entangled Coordination Networks Based on Charge‐Tunable Keggin‐Type Polyoxometalates
Authors: Hao Xiu‐Li , Ma Yuan‐Yuan , Wang Yong‐Hui , Xu Long‐Yang , Liu Fu‐Chen , Zhang Mao‐Mao , Li Yang‐Guang
Published: January 2014

Investigation into a hydrothermal reaction system with transition‐metal (TM) ions, 1,4‐bis(1,2,4‐triazol‐1‐lmethyl)benzene (BBTZ) and various charge‐tunable Keggin‐type polyoxometalates (POMs) led to the preparation of four new entangled coordination networks, [CoII(HBBTZ)(BBTZ)2.5][PMo12O40] (1), [CuI(BBTZ)]5[BW12O40]⋅H2O (2), [CuII(BBTZ)]3[AsWV3WVI9O40]⋅10 H2O (3), and [CuII5(BBTZ)7(H2O)6][P2W22Cu2O77(OH)2]⋅6 H2O (4). All compounds were characterized by using elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. The mixed valence of W centers in compound 3 was further confirmed by using XPS spectroscopy and bond‐valence sum calculations. In the structural analysis, the entangled networks of 1–4 demonstrate zipper‐closing packing, 3D polythreading, 3D polycatenation, and 3D self‐penetration, respectively. Moreover, with the enhancement of POM negative charges and the use of different TM types, the number of nodes in the coordination networks of 1–4 increased and the basic metal–organic building motifs changed from a 1D zipper‐type chain (in 1) to a 2D pseudorotaxane layer (in 2) to a 3D diamond‐like framework (in 3) and finally to a 3D self‐penetrating framework (in 4). The photocatalytic properties of compounds 1–4 for the degradation of methylene blue under UV light were also investigated; all compounds showed good catalytic activity and the photocatalytic activity order of Keggin‐type species was initially found to be {XMo12O40}>{XW12O40}>{XW12−nTMnO40}.
Entwicklung einer optimierten Schraubengeometrie für hochbeanspruchte Stahl‐Holz‐Verbindungen
Authors: Ringhofer Andreas , Brandner Reinhard , Schickhofer Gerhard
Published: January 2014

Der Beitrag behandelt die Optimierung der Geometrie von vorwiegend axial beanspruchten selbstbohrenden Holzschrauben für den Einsatz in einer Stahl‐Holz‐Laschenverbindung unter Zug parallel zur Faser. Mit Fokus auf den Stahlbruch werden der Kopf und Ansatzbereich des Gewindes adaptiert und die Veränderungen im Last‐Verformungsverhalten anhand von Prototypen versuchstechnisch an bauteilgroßen Laschenstößen und mittels einer numerischen Modellierung verifiziert. Es zeigen sich eine gegenüber herkömmlichen Schraubentypen um 2 bis 8 % gesteigerte Tragfähigkeit, eine Verlagerung des Versagens der Schraube von der Stahlblech‐Unterkante tiefer in das Holz sowie die Ausbildung eines Fließgelenks am Beginn der geschaffenen Freistrecke. Letzteres lässt einerseits eine homogenere Lastverteilung zwischen den Schrauben infolge eines erheblich gesteigerten Duktilitätspotenzials und andererseits eine Verbesserung des Tragverhaltens solcher Anschlüsse bei Langzeit‐ und Zugschwellbelastungen erwarten. Zudem wird ein Vorschlag für den Nettoquerschnittsnachweis für zugbeanspruchte Laschenstöße mit selbstbohrenden Holzschrauben unterbreitet.

Development of an optimized screw geometry for high‐stressed steel‐to‐timber joints

This paper deals with the geometrical optimization of mainly axially loaded self‐tapping screws applied in steel‐to‐timber joints under tension parallel to grain. Focusing on steel failure, the head geometry and the zone before the thread were adapted. Consequently, differences to standard products were verified by laboratory tests on full‐scale steel‐to‐timber joints and also by numerical modeling. A 2 to 8 % increase of load bearing resistance, a displacement of the location of screw failure deeper into the timber member as well as the development of a plastic hinge close to the head are the essential results of this study. Especially the yield deformation leads to a more homogenous load sharing between a group of screws, caused by an increased potential of ductility, and to an enhanced bearing behavior under long term as well as pulsating tensile loadings. In addition to that a proposal for the verification of the net cross‐section of tensile joints with self‐tapping screws is given.
Identification of novel candidate compounds targeting TrkB to induce apoptosis in neuroblastoma
Authors: Nakamura Yohko , Suganami Akiko , Fukuda Mayu , Hasan Md. Kamrul , Yokochi Tomoki , Takatori Atsushi , Satoh Shunpei , Hoshino Tyuji , Tamura Yutaka , Nakagawara Akira
Published: January 2014

Neuroblastoma (NB) is one of the most frequent solid tumors in children and its prognosis is still poor. The neurotrophin receptor TrkB and its ligand brain‐derived neurotrophic factor (BDNF) are expressed at high levels in high‐risk NBs and are involved in defining the poor prognosis of the patients. However, the TrkB targeting therapy has never been realized in the clinic. We performed an in silico screening procedure utilizing an AutoDock/grid computing technology in order to identify novel small chemical compounds targeting the BDNF‐binding domain of TrkB. For the first screening, a library of three million synthetic compounds was screened in silico and was ranked according to the Docking energy. The top‐ranked 37 compounds were further functionally screened for cytotoxicity by using NB cell lines. We have finally identified seven compounds that kill NB cells with the IC50 values of 0.07–4.6 μmol/L. The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay showed that these molecules induce apoptosis accompanied by p53 activation in NB cell lines. The candidate compounds and BDNF demonstrated an antagonistic effect on cell growth, invasion, and colony formation, possibly suggesting competition at the BDNF‐binding site of TrkB. The candidate compounds had tumor‐suppressive activity in xenograft and in vivo toxicity tests (oral and intravenous administrations) using mice, and did not show any abnormal signs. Using in silico Docking screening we have found new candidate TrkB inhibitors against high‐risk NBs, which could lead to new anti‐cancer drugs.
Kinetic Explanation for the Temperature Dependence of the Regioselectivity in the Hydroformylation of Neohexene
Authors: Güven Sabriye , Nieuwenhuizen Marko M. L. , Hamers Bart , Franke Robert , Priske Markus , Becker Marc , Vogt Dieter
Published: January 2014

The kinetics of Rh‐catalyzed neohexene hydroformylation were investigated with the bulky monodentate ligand tris(2,4‐di‐tert‐butylphenyl)phosphite. The hydrogenolysis of the Rh–acyl intermediate was identified as the rate‐limiting step for both the linear and the branched aldehydes. Rate equations for both aldehydes were derived and kinetic parameters were estimated. Increased aldehyde linearity at higher temperatures, frequently observed in hydroformylation, was elucidated by deuterioformylation experiments. These showed that at 100 °C the formation of linear Rh–alkyl was more reversible than the formation of the branched derivative. The ratio of linear to branched Rh–acyl species was determined by in situ high‐pressure IR spectroscopy experiments, which allowed the difference in the activation energies for the hydrogenolysis steps towards the aldehyde isomers to be quantified. The hydrogenolysis of Rh–acyl was found to be the step that caused the greatest temperature effect on the regioselectivity.
Solvent Migration in Microhydrated Aromatic Aggregates: Ionization‐Induced Site Switching in the 4‐Aminobenzonitrile–Water Cluster
Authors: Nakamura Takashi , Schmies Matthias , Patzer Alexander , Miyazaki Mitsuhiko , Ishiuchi Shun‐ichi , Weiler Martin , Dopfer Otto , Fujii Masaaki
Published: January 2014

The dependence of the preferred microhydration sites of 4‐aminobenzonitrile (4ABN) on electronic excitation and ionization is determined through IR spectroscopy of its clusters with water (W) in a supersonic expansion and through quantum chemical calculations. IR spectra of neutral 4ABN and two isomers of its hydrogen‐bonded (H‐bonded) 4ABN–W complexes are obtained in the ground and first excited singlet states (S0, S1) through IR depletion spectroscopy associated with resonance‐enhanced multiphoton ionization. Spectral analysis reveals that electronic excitation does not change the H‐bonding motif of each isomer, that is, H2O binding either to the CN or the NH site of 4ABN, denoted as 4ABN–W(CN) and 4ABN–W(NH), respectively. The IR spectra of 4ABN+–W in the doublet cation ground electronic state (D0) are measured by generating them either in an electron ionization source (EI‐IR) or through resonant multiphoton ionization (REMPI‐IR). The EI‐IR spectrum shows only transitions of the most stable isomer of the cation, which is assigned to 4ABN+–W(NH). The REMPI‐IR spectrum obtained through isomer‐selective resonant photoionization of 4ABN–W(NH) is essentially the same as the EI‐IR spectrum. The REMPI‐IR spectrum obtained by ionizing 4ABN–W(CN) is also similar to that of the 4ABN+–W(NH) isomer, but differs from that calculated for 4ABN+–W(CN), indicating that the H2O ligand migrates from the CN to the NH site upon ionization with a yield of 100 %. The mechanism of this CN→NH site‐switching reaction is discussed in the light of the calculated potential energy surface and the role of intracluster vibrational energy redistribution.
Stable Isolated Metal Atoms as Active Sites for Photocatalytic Hydrogen Evolution
Authors: Xing Jun , Chen Jian Fu , Li Yu Hang , Yuan Wen Tao , Zhou Ying , Zheng Li Rong , Wang Hai Feng , Hu P. , Wang Yun , Zhao Hui Jun , Wang Yong , Yang Hua Gui
Published: January 2014

The process of using solar energy to split water to produce hydrogen assisted by an inorganic semiconductor is crucial for solving our energy crisis and environmental problems in the future. However, most semiconductor photocatalysts would not exhibit excellent photocatalytic activity without loading suitable co‐catalysts. Generally, the noble metals have been widely applied as co‐catalysts, but always agglomerate during the loading process or photocatalytic reaction. Therefore, the utilization efficiency of the noble co‐catalysts is still very low on a per metal atom basis if no obvious size effect exists, because heterogeneous catalytic reactions occur on the surface active atoms. Here, for the first time, we have synthesized isolated metal atoms (Pt, Pd, Rh, or Ru) stably by anchoring on TiO2, a model photocatalystic system, by a facile one‐step method. The isolated metal atom based photocatalysts show excellent stability for H2 evolution and can lead to a 6–13‐fold increase in photocatalytic activity over the metal clusters loaded on TiO2 by the traditional method. Furthermore, the configurations of isolated atoms as well as the originality of their unusual stability were analyzed by a collaborative work from both experiments and theoretical calculations.
Tuning the Guest‐Binding Ability of a Helically Folded Capsule by In Situ Modification of the Aromatic Oligoamide Backbone
Authors: Lautrette Guillaume , Aube Christophe , Ferrand Yann , Pipelier Muriel , Blot Virginie , Thobie Christine , Kauffmann Brice , Dubreuil Didier , Huc Ivan
Published: January 2014

Starting from a previously described aromatic oligoamide helically folded capsule that binds tartaric acid with high affinity and diastereoselectivity, we demonstrate the feasibility of the direct in situ modification of the helix backbone, which results in a conformational change that reduces its affinity for guests by two orders of magnitude. Specifically, ring contraction of the central pyridazine unit into a pyrrole in the full helical sequence was investigated by using electrochemical and chemical processes. The sequence containing the pyrrole was synthesized independently in a convergent manner to ascertain its structure. The conformation of the pyrrolic folded capsule was elucidated in the solid state by X‐ray crystallography and in solution by using 1H and 13C NMR spectroscopy. Solution studies revealed an unanticipated solvent‐dependent equilibrium between the anti–anti and syn–syn conformations of the pyrrole ring with respect to its two adjacent pyridine units. Titrations of the pyrrole‐containing sequence monitored by 1H NMR spectroscopy confirmed the expected drop in affinity for tartaric acid and malic acid that arises from the conformation change in the backbone that follows the replacement of the pyridazine by a pyrrole. The reduction of the pyridazine to a pyrrole was characterized by cyclic voltammetry both on the entire sequence and on a shorter precursor. The lower cathodic potential of the precursor made its preparative‐scale electroreduction possible. Direct in situ modification of the pyridazine within the entire capsule sequence was achieved chemically by using zinc in acetic acid.
Folding‐Induced Folding: The Assembly of Aromatic Amide and 1,2,3‐Triazole Hybrid Helices
Authors: Wu Chun‐Fang , Li Zhi‐Ming , Xu Xiao‐Na , Zhao Zhi‐Xiong , Zhao Xin , Wang Ren‐Xiao , Li Zhan‐Ting
Published: January 2014

Folding‐induced folding for the construction of artificial hybrid helices from two different kinds of aromatic sequences is described. Linear compounds 1 a, 1 b, and 2, containing one aromatic amide trimer or pentamer and one or two aromatic 1,2,3‐triazole tetramers, have been designed and synthesized. The trimeric and pentameric amide segments are driven by intramolecluar NH⋅⋅⋅F hydrogen bonding to adopt a folded or helical conformation, whereas the triazole segment is intrinsically disordered. In organic solvents of low polarity, the amide foldamer segment induces the attached triazole segment(s) to fold through intramolecular stacking, leading to the formation of hybrid helices. The helical conformation of these hybrid sequences has been confirmed by 1H and 19F NMR spectroscopy, UV/Vis spectroscopy, circular dichroism (CD) experiments, and theoretical calculations. It was found that the amide pentamer exhibits a stronger ability to induce the folding of the attached triazole segment(s) compared with that of the shorter trimer. Enantiomers (R)‐3 and (S)‐3, which contain an R‐ or S‐(1‐naphthyl)ethylamino group at the end of a tetraamide segment, have also been synthesized. CD experiments showed that introduction of a chiral group caused the whole framework to produce a strong helicity bias. Density‐functional‐theory calculations on (S)‐3 suggested that this compound exists as a right‐handed (P) helix.
Label‐Free Measurements of the Diffusivity of Molecules in Lipid Membranes
Authors: Johansson Björn , Höök Fredrik , Klenerman David , Jönsson Peter
Published: January 2014

An important and characteristic property of a cell membrane is the lateral mobility of protein molecules in the lipid bilayer. This has conventionally been measured by labeling the molecules with fluorescent markers and monitoring their mobility by different fluorescence‐based techniques. However, adding the label to the studied molecule may affect the system, so it is an assumption in almost all experiments that the measured mobility of the biomolecule with its label is the same as that of the unlabeled molecule. However, this assumption is rarely tested due to a lack of suitable methods. In this work, a new technique to perform label‐free diffusivity measurements is developed and used to measure the effect of the label for two common protein–lipid systems: 1) streptavidin (SA) coupled to a supported lipid bilayer (SLB) through biotinylated lipids and 2) the extracellular part of the T‐cell adhesion protein CD2, coupled to an SLB through histidine tags to nickel‐chelating lipids. A measurable (≈12 %) decrease in diffusivity is found for both labeled proteins, even though the molecular mass of the label is almost 100 times smaller than those of the proteins (≈50 kDa). The results illustrate the importance of being able to study different biophysical properties of cell membranes and their mimics without relying on fluorescent labels, especially if fluorescent labeling is difficult or is expected to affect the nature of the intermolecular interactions being studied.
An exploration of social identity: The structure of the BBC news‐sharing community on Twitter
Authors: Adebayo Julius , Tiziana Musso , Virdee Kawandeep , Friedman Casey , Yaneer Bar‐Yam
Published: January 2014

Online social media influence the flow of news and other information, potentially altering collective social action while generating a large volume of data useful to researchers. Mapping these networks may make it possible to predict the course of social and political movements, technology adoption, and economic behavior. Here, we map the network formed by Twitter users sharing British Broadcasting Corporation (BBC) articles. The global audience of the BBC is primarily organized by language with the largest linguistic groups receiving news in English, Spanish, Russian, and Arabic. Members of the network primarily “follow” members sharing articles in the same language, and these audiences are primarily located in geographical regions where the languages are native. The one exception to this rule is a cluster interested in Middle East news which includes both Arabic and English speakers. We further analyze English‐speaking users, which differentiate themselves into four clusters: one interested in sports, two interested in United Kingdom (UK) news—with word usage suggesting this reflects political polarization into Conservative and Labour party leanings—and a fourth group that is the English speaking part of the group interested in Middle East news. Unlike the previously studied New York Times news sharing network the largest scale structure of the BBC network does not include a densely connected group of globally interested and globally distributed users. The political polarization is similar to what was found for liberal and conservative groups in the New York Times study. The observation of a primary organization of the BBC audience around languages is consistent with the BBC's unique role in history as an alternative source of local news in regions outside the UK where high quality uncensored news was not available. © 2014 Wiley Periodicals, Inc. Complexity 19: 55–63, 2014
The effect of synchronous firing on the clustering dynamics of social amoebae
Authors: Yang Yipeng , Li Y. Charles
Published: January 2014

A discrete model for computer simulations of the clustering dynamics of social amoebae is presented. This model incorporates the wavelike propagation of extracellular signaling of 3′–5′‐cyclic adenosine monophosphate (cAMP), the sporadic firing of cells at early stage of aggregation, the signal relaying as a response to stimulus, and the inertia and purposeful random walk of the cell movement. It is found that the sporadic firing below the threshold of cAMP concentration plays an important role because it allows time for the cells to form synchronous firing right before the stage of aggregation, and the synchronous firing is critical for the onset of clustering behavior of social amoebae. A Monte‐Carlo simulation was also run which showed the existence of potential equilibriums of mean and variance of aggregation time. The simulation result of this model could well reproduce many phenomena observed by actual experiments. © 2013 Wiley Periodicals, Inc. Complexity 20: 16–26, 2014
Synthesis, Characterization, and Crystal Structures of Scorpionate Complexes with the Hydrotris[3‐(2′‐thienyl)pyrazol‐1‐yl]borate Ligand
Authors: Pettinari Claudio , Marchetti Fabio , Orbisaglia Serena , Palmucci Jessica , Pettinari Riccardo , Di Nicola Corrado , Skelton Brian W. , White Allan H.
Published: January 2014

Six scorpionate complexes of group 10–12 metal elements (CuI, CuII, ZnII, and CdII) containing the anionic hydrotris[3‐(2′‐thienyl)pyrazol‐1‐yl]borate (TpTn) ligand were prepared from the reaction of the thallium(I) salt of TpTn with the corresponding metal acceptors in chloroform solution. The air‐ and heat‐stable complexes were characterized by analytical and spectroscopic methods (IR, conductivity, ESI‐MS, 1H NMR and 13C NMR solution data) and structurally characterized by single‐crystal X‐ray studies. The ZnII complexes [Zn(TpTn)X] (X = Cl or Br) contain a tripodal tridentate TpTn ligand, in which the tetrahedral metal environment is completed by a halide; in [Cd(TpTn)2], cadmium is found in an octahedral environment coordinated by two TpTn ligands. In [Cu(TpTn)(PPh3)]·CHCl3 and [Cu(TpTn)(OC(O)CH3)], TpTn is also coordinated in the tripodal fashion, in which the copper environment is completed by a triphenylphosphine ligand in the former complex and by a symmetrically coordinated bidentate acetate ligand occupying trans‐coordinated sites in the latter complex. The reaction of [Zn(TpTn)X] with an excess amount of [Tl(TpTn)] in MeOH yielded [Zn(TpTn)2] and TlX, whereas the reaction of [Zn(TpTn)X] with Na(Tp) gave [Zn(TpTn)2] and [Zn(Tp)2] in a 1:1 molar ratio but not [Zn(TpTn)(Tp)]. By contrast, the reaction of [Tl(TpTn)] with copper(II) sulfate monohydrate in chloroform gave a green powder, which was identified as the [(Hpz3Tn)4CuSO4](∞|∞) coordination polymer containing OSO2O bridging sulfate groups and four coordinated pyrazole ligands on each metal center, the latter of which arises from the decomposition of the TpTn ligand through B–N bond breaking. Similarly, the interaction between [Tl(TpTn)] and platinum(II) diiodide in chloroform/DMSO proceeded through TpTn decomposition to afford a monomeric trans‐[(Hpz3Tn)2PtI2]·2(CH3)2SO complex, wherein two neutral pyrazole ligands are coordinated to the PtII center.
A Metal‐Mediated Base Pair with a [2+1] Coordination Environment
Authors: Richters Tim , Müller Jens
Published: January 2014

A silver(I)‐mediated base pair based on azole‐derived ligands only was devised. The base pair comprises the monodentate imidazole nucleoside and a nucleoside carrying the new bidentate ligand 4‐[(1H‐1,2,4‐triazol‐1‐yl)methyl]‐1H‐1,2,3‐triazole. The silver(I) ion is hence coordinated in a trigonal planar [2+1] environment. A representative DNA duplex comprising the new base pair is stabilized by 6 °C upon binding one equivalent of silver(I). CD spectroscopy was used to confirm that the duplex adopts the canonical B‐type conformation. The base pair represents the first example of a metal‐mediated base pair with a [2+1] coordination environment.
Differential Functionalization of 1,6‐Naphthyridin‐2(1H)‐ones through Sequential One‐Pot Suzuki–Miyaura Cross‐Couplings
Authors: Montoir David , Tonnerre Alain , Duflos Muriel , Bazin Marc‐Antoine
Published: January 2014

A practical synthesis of 7‐chloro‐3‐iodo‐1‐methyl‐1,6‐naphthyridin‐2(1H)‐one is described that starts from 2‐chloro‐4‐(methylamino)nicotinaldehyde. The dihalo compound then undergoes sequential, site‐selective Suzuki–Miyaura cross‐coupling reactions to afford highly functionalized 1,6‐naphthyridones in good yields.
Hazardous processes and events from glacier and permafrost areas: lessons from the Chilean and Argentinean Andes
Authors: Iribarren Anacona Pablo , Mackintosh Andrew , Norton Kevin Patrick
Published: January 2014

Glacier and permafrost hazards such as glacial‐lake outburst floods and rock–ice avalanches cause significant socio‐economic damages worldwide, and these processes may increase in frequency and magnitude if the atmospheric temperature rises. In the extratropical Andes nearly 200 human deaths were linked to these processes during the twentieth century. We analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio‐economic damages in this region in historic time (including glacial lake outburst floods, ice and rock–ice avalanches and lahars) to unravel their causes and geomorphological impacts. In the extratropical Andes, at least 15 ice‐dammed lakes and 16 moraine‐dammed lakes have failed since the eighteenth century, causing dozens of floods. Some floods rank amongst the largest events ever recorded (5000 × 106 m3 and 229 × 106 m3, respectively). Outburst flood frequency has increased in the last three decades, partially as a consequence of long‐term (decades to centuries) climatic changes, glaciers shrinkage, and lake growth. Short‐term (days to weeks) meteorological conditions (i.e. intense and/or prolonged rainfall and high temperature that increased meltwater production) have also triggered outburst floods and mass movements. Enormous mass failures of glaciers and permafrost (> 10 × 106 m3) have impacted lakes, glaciers, and snow‐covered valleys, initiating chain reactions that have ultimately resulted in lake tsunamis and far‐reaching (> 50 km) flows. The eruption of ice‐covered volcanoes has also caused dozens of damaging lahars with volumes up to 45 × 106 m3. Despite the importance of these events, basic information about their occurrence (e.g. date, causes, and geomorphological impact), which is well established in other mountain ranges, is absent in the extratropical Andes. A better knowledge of the processes involved can help to forecast and mitigate these events. Copyright © 2014 John Wiley & Sons, Ltd.
Geochronology and geochemistry of the Dashui adakitic granitoids in the western Qinling Orogen, central China: implications for Triassic tectonic setting
Authors: Han Jin‐Sheng , Yao Jun‐Ming , Chen Yan‐Jing
Published: January 2014

The Dashui porphyry granitoids in the western Qinling Orogen are spatially associated with the Dashui gold deposit, but their ages and tectonic setting have not been well defined yet in previous studies. This paper reports the results and understandings obtained from our original study in geochronology and isotope and element geochemistry. SHRIMP zircon U–Pb dating yielded ages of 213.7 ± 2.7 Ma for granitic stock and 215.1 ± 2.5 and 210.2 ± 1.6 Ma for granitic dikes. The granitoids are characterized by high LREE but low HREE and HFSE. They have (87Sr/86Sr)i ratios of 0.706 to 0.709 and εNd(t) values of −5.3 to −7.6. The majority of zircons in the Dashui granitoids have εHf(t) values ranging from −6.2 to 6.7 and TDM2(Hf) ages from 743 to 1464 Ma. The isotope signatures, together with La/Y and Mg# values, show that the magmas are mainly sourced from partial melting of a subducted slab, and possibly assimilated immature sediments during upward migration. Thus, the Dashui granitoids most likely formed in a volcanic arc where supra‐subduction zone melts assimilated lower crustal material no later than 215 Ma. Copyright © 2014 John Wiley & Sons, Ltd.
Identification of the Active Sites for Low Temperature CO Oxidation over Nanocrystalline Co3O4 Catalysts
Authors: Liu Chang‐Xiang , Liu Qian , Huang Xi‐Gen , Nie Xu‐Liang , Huang Zhong
Published: January 2014

The microstructural properties of dry‐grinding derived Co3O4 catalysts pretreated under different atmospheres, in relation to the activities on CO oxidation were investigated. The Co3O4 synthesized by soft reactive grinding and pretreated with O2 resulted in the best activity, with 100% conversion of CO at −52 °C, superior to that of Co3O4 pretreated with He. To find out the active sites on Co3O4 for low temperature CO oxidation, the characterizations of the cobalt oxides had been investigated by means of N2 physisorption, XRD, TEM, H2‐TPR, CO‐titration, XPS and O2‐TPD technologies. XPS of Co2p results show that it is difficult to ascribe the difference in catalytic performance to the surface concentration of active Co3+ sites. A correlation between the activity and the CO‐titration and O2‐TPD results for Co3O4 reveals that a high abundance of readily accessible superficial electrophilic oxygen (O−) species is important for achieving a high activity. Therefore, CO oxidation takes place on the surface active oxygen sites in Co3O4 crystallites via the suprafacial mechanism.
Gadolinium‐free extracellular MR contrast agent for tumor imaging
Authors: Nofiele Joris Tchouala , Haedicke Inga E. , Zhu Yong Le K. , Zhang Xiao‐an , Cheng Hai‐Ling Margaret
Published: January 2014

Purpose

To evaluate a new formulation of manganese porphyrin as a potential gadolinium (Gd)‐free extracellular magnetic resonance imaging (MRI) contrast agent for dynamic contrast‐enhanced (DCE) MRI of tumors.

Materials and Methods

A previously reported new contrast agent, MnTCP, was evaluated in six female tumor‐bearing nude rats. MRI was performed on a 3 T clinical scanner 3 to 4 weeks after inoculation of breast tumor cells in the mammary fat pads. Gd‐DTPA was injected intravenously, followed by injection of MnTCP at least 2 hours later (both at 0.05 mmol/kg). T1 relaxation time measurements and DCE‐MRI were performed.

Results

Enhancement and clearance patterns were visually similar between MnTCP and Gd‐DTPA. However, relative R1 increases in all 11 tumors were larger for MnTCP over 60 minutes postcontrast, the difference being significant as late as 20 minutes (R1post/R1pre = 1.42 ± 0.15 for MnTCP vs. 1.20 ± 0.08 for Gd‐DTPA, P < 0.05). R1‐related effects for MnTCP were largely reduced after 60 minutes (R1post/R1pre = 1.13 ± 0.07) and completely gone within 24 hours (R1post/R1pre = 0.97 ± 0.06). DCE‐MRI revealed a consistently larger (1.5 to over 2‐fold) peak enhancement and higher values of the steepest slope, time‐to‐peak, and AUC60 in all tumors with MnTCP (P < 0.01).

Conclusion

MnTCP is an alternative to extracellular Gd agents for tumor imaging, offering sensitive detection and rapid renal clearance. J. Magn. Reson. Imaging 2015;41:397–403.© 2013 Wiley Periodicals, Inc.
Acid Resistance in Francisella tularensis
Authors: Adcock Noreen J. , Morris Brian J. , Rice Eugene W.
Published: January 2014

Francisella tularensis, the etiologic agent of tularemia, can survive under acidic conditions. Tularemia can be acquired by several routes, including by ingestion of contaminated food or water. While acid resistance is usually associated with a low oral infective dose (ID), the ID for gastrointestinal illness is quite high. In this study, four strains of F. tularensis ssp. tularensis (type A) and four strains of F. tularensis ssp. holarctica (type B) were examined for innate acid resistance and the ability to survive in synthetic gastric fluid (SGF) under in vitro conditions similar to passage through the human stomach. Survival for all strains was significantly less in pH 2.5 SGF than in pH 2.5 phosphate‐buffered saline and pH 4.0 SGF. Attenuated strains were consistently less resistant. Type B strains are most often associated with waterborne outbreaks and were examined after storage in natural water. Low‐nutrient preadaptation resulted in increased resistance. Although F. tularensis can persist under certain acidic conditions, it is sensitive to conditions replicating the fasting human stomach. This may help explain the high ID required for gastrointestinal infections.
Nonlinear model predictive control for path following problems
Authors: Yu Shuyou , Li Xiang , Chen Hong , Allgöwer Frank
Published: January 2014

This paper presents a general nonlinear model predictive control scheme for path following problems. Path following problem of nonlinear systems is transformed into a parameter‐dependent regulation problem. Sufficient conditions for recursive feasibility and asymptotic convergence of the given scheme are presented. Furthermore, a polytopic linear differential inclusion‐based method of choosing a suitable terminal penalty and the corresponding terminal constraint are proposed. To illustrate the implementation of the nonlinear model predictive control scheme, the path following problem of a car‐like mobile robot is discussed, and the control performance is confirmed by simulation results. Copyright © 2014 John Wiley & Sons, Ltd.