bluuebunny/crossref_metadata_2025 huggingface dataset:
A large‐scale view of Space Technology 5 magnetometer response to solar wind drivers
Authors: Knipp D. J. , Kilcommons L. M. , Gjerloev J. , Redmon R. J. , Slavin J. , Le G.
Published: March 2015

In this data report we discuss reprocessing of the Space Technology 5 (ST5) magnetometer database for inclusion in NASA's Coordinated Data Analysis Web (CDAWeb) virtual observatory. The mission consisted of three spacecraft flying in elliptical orbits, from 27 March to 27 June 2006. Reprocessing includes (1) transforming the data into the Modified Apex Coordinate System for projection to a common reference altitude of 110 km, (2) correcting gain jumps, and (3) validating the results. We display the averaged magnetic perturbations as a keogram, which allows direct comparison of the full‐mission data with the solar wind values and geomagnetic indices. With the data referenced to a common altitude, we find the following: (1) Magnetic perturbations that track the passage of corotating interaction regions and high‐speed solar wind; (2) unexpectedly strong dayside perturbations during a solstice magnetospheric sawtooth oscillation interval characterized by a radial interplanetary magnetic field (IMF) component that may have enhanced the accompanying modest southward IMF; and (3) intervals of reduced magnetic perturbations or “calms,” associated with periods of slow solar wind, interspersed among variable‐length episodic enhancements. These calms are most evident when the IMF is northward or projects with a northward component onto the geomagnetic dipole. The reprocessed ST5 data are in very good agreement with magnetic perturbations from the Defense Meteorological Satellite Program (DMSP) spacecraft, which we also map to 110 km. We briefly discuss the methods used to remap the ST5 data and the means of validating the results against DMSP. Our methods form the basis for future intermission comparisons of space‐based magnetometer data.
Analysis of temperature versus density plots and their relation to the LLBL formation under southward and northward IMF orientations
Authors: Němeček Z. , Šafránková J. , Kruparova O. , Přech L. , Jelínek K. , Dušík Š. , Šimůnek J. , Grygorov K. , Shue J.‐H.
Published: March 2015

The paper reports a clear dependence of a basic structure of two sublayers of the low‐latitude boundary layer (LLBL) on northward and southward interplanetary magnetic field (IMF) orientations. Regardless of different processes responsible for a formation and evolution of the entire LLBL, the outer part of the LLBL is significantly influenced by the sign of the IMF BZ component. Under northward IMF conditions this layer is present, whereas it is missing during a southward pointing IMF. This behavior can be understood in terms of a motion of reconnection spots due to the changes of the orientation of the magnetosheath magnetic field in the vicinity of the magnetopause. Our case and statistical studies demonstrate that the changes of the LLBL structure can be observed in the subsolar region as well as on flanks near the dawn‐dusk meridian. Moreover, the study emphasizes a role of magnetosheath magnetic field variations on the boundary layer formation.
A computational and theoretical investigation of nonlinear wave‐particle interactions in oblique whistlers
Authors: Nunn David , Omura Yoshiharu
Published: March 2015

Most previous work on nonlinear wave‐particle interactions between energetic electrons and VLF waves in the Earth's magnetosphere has assumed parallel propagation, the underlying mechanism being nonlinear trapping of cyclotron resonant electrons in a parabolic magnetic field inhomogeneity. Here nonlinear wave‐particle interaction in oblique whistlers in the Earth's magnetosphere is investigated. The study is nonself‐consistent and assumes an arbitrarily chosen wave field. We employ a “continuous wave” wave field with constant frequency and amplitude, and a model for an individual VLF chorus element. We derive the equations of motion and trapping conditions in oblique whistlers. The resonant particle distribution function, resonant current, and nonlinear growth rate are computed as functions of position and time. For all resonances of order n, resonant electrons obey the trapping equation, and provided the wave amplitude is big enough for the prevailing obliquity, nonlinearity manifests itself by a “hole” or “hill” in distribution function, depending on the zero‐order distribution function and on position. A key finding is that the n = 1 resonance is relatively unaffected by moderate obliquity up to 25°, but growth rates roll off rapidly at high obliquity. The n = 1 resonance saturates due to the adiabatic effect and here reaches a maximum growth at ~20 pT, 2000 km from the equator. Damping due to the n = 0 resonance is not subject to adiabatic effects and maximizes at some 8000 km from the equator at an obliquity ~55°.
Processes controlling mid‐water column oxygen minima over the Texas‐Louisiana shelf
Authors: Zhang Wenxia , Hetland Robert D. , DiMarco Steven F. , Fennel Katja
Published: March 2015

We investigate distributions of dissolved oxygen over the Texas‐Louisiana shelf using spatially highly resolved observations in combination with a regional circulation model with simple oxygen dynamics. The observations were collected using a towed, undulating CTD during the Mechanisms Controlling Hypoxia (MCH) program. Mid‐water oxygen minimum layers (dissolved oxygen lower than 3.2 mL L−1) were detected in many transects. These oxygen minimum layers are connected with the bottom boundary layer and follow the pycnocline seaward as a tongue of low oxygen into the mid‐water column. T‐S diagrams highlighting the low oxygen minima in both observations and simulations imply direct connections between low‐oxygen bottom water and the oxygen minimum layer. The dynamics of these oxygen minimum layers in the mid‐water column are examined using a three‐dimensional hydrodynamic model, based on the Regional Ocean Modeling System (ROMS). Convergence within the bottom boundary layer relative to density surfaces is calculated, results show that there is a convergence in the bottom boundary layer at the location where the pycnocline intersects the bottom. Buoyancy advection forced by bottom Ekman transport creates this convergent flow, and the corresponding low‐oxygen intrusion. Similar intrusions of near‐bottom water into the pycnocline are observed in other regions. The presence of hypoxia within the bottom boundary layer in the northern Gulf of Mexico creates a unique situation in which these intrusions are also associated with low dissolved oxygen.
Altitude‐resolved shortwave and longwave radiative effects of desert dust in the Mediterranean during the GAMARF campaign: Indications of a net daily cooling in the dust layer
Authors: Meloni D. , Junkermann W. , di Sarra A. , Cacciani M. , De Silvestri L. , Di Iorio T. , Estellés V. , Gómez‐Amo J. L. , Pace G. , Sferlazzo D. M.
Published: March 2015

Desert dust interacts with shortwave (SW) and longwave (LW) radiation, influencing the Earth radiation budget and the atmospheric vertical structure. Uncertainties on the dust role are large in the LW spectral range, where few measurements are available and the dust optical properties are not well constrained. The first airborne measurements of LW irradiance vertical profiles over the Mediterranean were carried out during the Ground‐based and Airborne Measurements of Aerosol Radiative Forcing (GAMARF) campaign, which took place in spring 2008 at the island of Lampedusa. The experiment was aimed at estimating the vertical profiles of the SW and LW aerosol direct radiative forcing (ADRF) and heating rates (AHR), taking advantage of vertically resolved measurements of irradiances, meteorological parameters, and aerosol microphysical and optical properties. Two cases, characterized respectively by the presence of a homogeneous dust layer (3 May, with aerosol optical depth, AOD, at 500 nm of 0.59) and by a low aerosol burden (5 May, with AOD of 0.14), are discussed. A radiative transfer model was initialized with the measured vertical profiles and with different aerosol properties, derived from measurements or from the literature. The simulation of the irradiance vertical profiles, in particular, provides the opportunity to constrain model‐derived estimates of the AHR. The measured SW and LW irradiances were reproduced when the model was initialized with the measured aerosol size distributions and refractive indices. For the dust case, the instantaneous (solar zenith angle, SZA, of 55.1°) LW‐to‐SW ADRF ratio was 23% at the surface and 11% at the top of the atmosphere (TOA), with a more significant LW contribution on a daily basis (52% at the surface and 26% at TOA), indicating a relevant reduction of the SW radiative effects. The AHR profiles followed the aerosol extinction profile, with comparable peaks in the SW (0.72 ± 0.11 K d−1) and in the LW (−0.52 ± 0.12 K d−1) for the considered SZA. On a daily basis, the absolute value of the heating rate was larger in the LW than in the SW, producing a net cooling effect at specific levels. These are quite unexpected results, emphasizing the important role of LW radiation.
An observational analysis of warm‐sector rainfall characteristics associated with the 21 July 2012 Beijing extreme rainfall event
Authors: Zhong Lingzhi , Mu Rong , Zhang Dalin , Zhao Ping , Zhang Zhiqiang , Wang Nan
Published: March 2015

An observational analysis of the multiscale processes leading to the extreme rainfall event in Beijing on 21 July 2012 is performed using rain gauge records, Doppler radar, and satellite products, radiosondes, and atmospheric analysis. This rainstorm process included two heavy rainfall stages in the early afternoon [1300–1400 Beijing Standard time (BST) (0500–0600 UTC)] and the evening (1600–1900 BST), respectively. The first stage exhibited warm‐sector rainfall characteristics as it occurred under low‐level warm and moist southeasterly flows ahead of a synoptic‐scale vortex and a cold front. When the southeasterly flows turned northeastward along a southwest‐northeast oriented mountain range in western Beijing, mesoscale convergence centers formed on the windward side of the mountain range in the early afternoon, initiating moist convection. Radar echo showed a northeastward propagation as these flows extended northward. Despite the shallowness of moist convection in the warm sector, atmospheric liquid water content showed the rapid accumulation, and a large amount of supercooled water and/or ice particles was possibly accumulated above the melting level. These appeared to contribute to the occurrence of the largest rainfall rate. During the second stage, as the synoptic‐scale vortex moved across Beijing, with southeastward intrusion of its northwesterly flows, the vortex‐associated lifting caused the generation of strong updrafts aloft and formed deep convection. This facilitated the further accumulation of supercooled water and/or ice particles above the melting level. Radar echo propagated southeastward. Liquid water showed a decrease in the lower troposphere, and there were strong downdrafts due to evaporation of liquid water particles, which resulted in the relatively weak hourly rainfall rates.
New model fit functions of the plasmapause location determined using THEMIS observations during the ascending phase of Solar Cycle 24
Authors: Cho Junghee , Lee Dae‐Young , Kim Jin‐Hee , Shin Dae‐Kyu , Kim Kyung‐Chan , Turner Drew
Published: March 2015

It is well known that the plasmapause is influenced by the solar wind and magnetospheric conditions. Empirical models of its location have been previously developed such as those by O'Brien and Moldwin (2003) and Larsen et al. (2006). In this study, we identified the locations of the plasmapause using the plasma density data obtained from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. We used the data for the period (2008–2012) corresponding to the ascending phase of Solar Cycle 24. Our database includes data from over a year of unusually weak solar wind conditions, correspondingly covering the plasmapause locations in a wider L range than those in previous studies. It also contains many coronal hole stream intervals during which the plasmasphere is eroded and recovers over a timescale of several days. The plasmapause was rigorously determined by requiring a density gradient by a factor of 15 within a radial distance of 0.5 L. We first determined the statistical correlation of the plasmapause locations with several solar wind parameters as well as geomagnetic indices. We found that the plasmapause locations are well correlated with the solar wind speed and the interplanetary magnetic field Bz, therefore the y component of the convective electric field, and some energy coupling functions such as the well‐known Akasofu's epsilon parameter. The plasmapause locations are also highly correlated with the geomagnetic indices, Dst, AE, and Kp, as recognized previously. Finally, we suggest new model fit functions for the plasmapause locations in terms of the solar wind parameters and geomagnetic indices. When applied to a new data interval outside the model training interval, our model fit functions work better than existing ones. The new model fit functions developed here extend the range of conditions from those used in previous works.
Hematite Films Decorated with Nanostructured Ferric Oxyhydroxide as Photoanodes for Efficient and Stable Photoelectrochemical Water Splitting
Authors: Yu Qing , Meng Xianguang , Wang Tao , Li Peng , Ye Jinhua
Published: March 2015

Hematite photoanodes are decorated with nanostructured FeOOH by photoelectrodeposition. An obvious cathodic shift in the photocurrent onset potential is observed, while four‐times enhancement of photocurrent density enhancement is acheived with FeOOH present. This can be ascribed to the high reaction area for the structure and high electrocatalytic activity of nanostructured FeOOH, which increases the amount of photogenerated holes involved in the water oxidation reaction and accelerates the kinetics of water oxidation. Furthermore, the obtained Fe2O3/FeOOH photoanode achieves considerable O2 evolution rate (10.1 μmol h−1 cm−2) under AM 1.5 G illumination and is maintained for as long as 70 h. The Fe2O3/FeOOH films show visible light response, high photocurrent density, and long‐term stability, and they are well qualified photoanode materials and a promising candidate for photoelectrochemical water splitting.
Materials Displaying Neural Growth Factor Gradients and Applications in Neural Differentiation of Embryoid Body Cells
Authors: Delalat Bahman , Mierczynska Agnieszka , Ghaemi Soraya Rasi , Cavallaro Alex , Harding Frances J. , Vasilev Krasimir , Voelcker Nicolas H.
Published: March 2015

The critical growth factor density required to support neural lineage generation from mouse embryonic stem cells is assessed by constructing a surface density gradient of immobilized nerve growth factor (NGF) from a plasma polymer film base. A chemical surface gradient varying from high hydroxyl group density to high aldehyde group density is prepared through diffusion‐controlled plasma polymerization of two monomers (ethanol and propionaldehyde) under a moving mask. NGF density gradients are then produced by reductive amination with the aldehyde groups on the plasma polymer surface. Mouse embryoid body derived (mEB) cell differentiation on the gradient surface is evaluated by immunofluorescence staining against Nestin. mEB cell density and the percentage of Nestin‐positive cells increase with increasing NGF density up to a critical value corresponding to 52.9 ng cm−2, above which cell attachment and differentiation do not increase further. This gradient‐based screening approach allows the growth factor surface densities to be optimized for biomaterials intended for cell differentiation or expansion, which is highly relevant to creating efficient manufacture processes for cell therapies.
Complex Photonic Structures for Light Harvesting
Authors: Burresi Matteo , Pratesi Filippo , Riboli Francesco , Wiersma Diederik Sybolt
Published: March 2015

Over the last few years, micro‐ and nanophotonics have roused a strong interest in the scientific community for their promising impact on the development of novel kinds of solar cells. Certain thin‐ and ultrathin‐film solar cells are made of innovative, often cheap, materials which suffer from a low energy conversion efficiency. Light‐trapping mechanisms based on nanophotonics principles are particularly suited to enhance the absorption of electromagnetic waves in these thin media without changing the material composition. In this review, the latest results achieved in this field are reported, with particular attention to the realization of prototypes, spanning from deterministic to disordered photonic architectures, and from dielectric to metallic nanostructures.
Synthesis of 2,6‐Dihalogenated Purine Nucleosides by Thermostable Nucleoside Phosphorylases
Authors: Zhou Xinrui , Szeker Kathleen , Jiao Lin‐Yu , Oestreich Martin , Mikhailopulo Igor A. , Neubauer Peter
Published: March 2015

The enzymatic transglycosylation of 2,6‐dichloropurine (26DCP) and 6‐chloro‐2‐fluoropurine (6C2FP) with uridine, thymidine and 1‐(β‐D‐arabinofuranosyl)‐uracil as the pentofuranose donors and recombinant thermostable nucleoside phosphorylases from G. thermoglucosidasius or T. thermophilus as biocatalysts was studied. Selection of 26DCP and 6C2FP as substrates is determined by their higher solubility in aqueous buffer solutions compared to most natural and modified purines and, furthermore, synthesized nucleosides are valuable precursors for the preparation of a large number of biologically important nucleosides. The substrate activity of 26DCP and 6C2FP in the synthesis of their ribo‐ and 2′‐deoxyribo‐nucleosides was closely similar to that of related 2‐amino‐ (DAP), 2‐chloro‐ and 2‐fluoroadenines; the efficiency of the synthesis of β‐D‐arabinofuranosides of 26DCP and 6C2FP was lower vs. that of DAP under similar reaction conditions. For a convenient and easier recovery of the biocatalysts, the thermostable enzymes were immobilized on MagReSyn® epoxide beads and the biocatalyst showed high catalytic efficiency in a number of reactions. As an example, 6‐chloro‐2‐fluoro‐(β‐D‐ribofuranosyl)‐purine (9), a precursor of various antiviral and antitumour drugs, was synthesized by the immobilized enzymes at 60 °C under high substrate concentrations (uridine:purine ratio of 2:1, mol). The synthesis was successfully scaled‐up [uridine (2.5 mmol), base (1.25 mmol); reaction mixture 50 mL] to afford 9 in 60% yield. The reaction reveals the great practical potential of this enzymatic method for the efficient production of modified purine nucleosides of pharmaceutical interest.

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Chemo‐Controlled Cross‐Coupling of Di(hetero)aryl Disulfides with Grignard Reagents: CC vs. CS Bond Formation
Authors: Du Bao‐Xin , Quan Zheng‐Jun , Da Yu‐Xia , Zhang Zhang , Wang Xi‐Cun
Published: March 2015

A general protocol for the chemoselectivity‐controlled CC and CS coupling reactions of di(hetero)aryl disulfides with Grignard reagents catalyzed by ferrocene and palladium acetate has been developed. Ferrocene favored the formation of CS coupled products at low temperature, whereas CC bond couplings were favored when palladium acetate was used. All the reactions proceeded with excellent chemoselectivity and in good yields under mild conditions, and a library of molecules with pyridine and pyrimidine scaffolds was produced.

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Enantiopure Helical Ferrocene–Triazole–Quinone Triads: Synthesis and Properties
Authors: Hoyo Ana M. del , Latorre Alfonso , Díaz Raúl , Urbano Antonio , Carreño M. Carmen
Published: March 2015

The copper(I)‐catalyzed (2+3) cycloaddition between azido (or azidomethylene) ferrocenes and enantiopure (P)‐14‐(p‐ethynylphenyl)‐[5]‐tetrahydro‐helicenequinone afforded ferrocene–triazole–quinone triads, whereas diazido ferrocenes gave rise to the corresponding double triads. In reactions with 1,1′‐diazidoferrocene, the use of CuI/CH3CN or CuSO4/sodium ascorbate/THF conditions allowed the divergent formation of an open chain dimeric structure or a 1,4‐diaza‐[4]‐ferrocenophane resulting from an intramolecular oxidative coupling of the two triazole units formed after the double cycloaddition process.

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Direct Coupling of Arylacetonitriles and Primary Alcohols to α‐Alkylated Arylacetamides with Complete Atom Economy Catalyzed by a Rhodium Complex–Triphenylphosphine– Potassium Hydroxide System
Authors: Li Feng , Zou Xiaoyuan , Wang Nana
Published: March 2015

A direct synthesis of α‐alkylated arylacetamides from arylacetonitriles and primary alcohols has been accomplished for the first time. In the presence of the rhodium complex [Rh(cod)Cl]2/triphenylphosphine/potassium hydroxide system, the desired α‐alkylated arylacetamides were obtained in 74–92% yield under microwave conditions. The experimental results in this paper are in sharp contrast with previous reports, where the coupling of arylacetonitriles and primary alcohols produced the α‐alkylated arylacetonitriles. Mechanistic investigations show that arylacetonitriles are first α‐alkylated with primary alcohols to produce α‐alkylated arylacetonitriles, which are further hydrated with the water resulting from the α‐alkylation step to produce α‐alkylated arylacetamides. More importantly, this research shows the potential of developing completely atom‐economical reactions that involve the hydrogen autotransfer (or hydrogen borrowing) process.

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Rhodium‐Catalyzed Decarbonylative Direct Olefination of Arenes with Vinyl Carboxylic Acids
Authors: Qiu Ruiying , Zhang Lingjuan , Xu Conghui , Pan Yixiao , Pang Hongze , Xu Lijin , Li Huanrong
Published: March 2015

A rhodium(I)‐catalyzed direct CH bond olefination of pyridyl‐substituted arenes with readily available vinyl carboxylic acids has been realized. This reaction occurred efficiently without the need for any external oxidant, affording the ortho‐olefinated products in high yields and excellent regioselectivities. Diversely substituted vinyl carboxylic acids behaved as efficient olefination reagents under the reaction conditions, and a range of functional groups in both coupling partners was well tolerated. Mechanistic studies indicated that a decarbonylation step is involved in this catalytic process, and pivalic anhydride [(t‐BuCO)2O] acts as the activator of the carboxylic acids for the in situ generation of highly active anhydrides.

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Voxel‐based morphometric magnetic resonance imaging (MRI) postprocessing in MRI‐negative epilepsies
Authors: Wang Z. Irene , Jones Stephen E. , Jaisani Zeenat , Najm Imad M. , Prayson Richard A. , Burgess Richard C. , Krishnan Balu , Ristic Aleksandar , Wong Chong H. , Bingaman William , Gonzalez‐Martinez Jorge A. , Alexopoulos Andreas V.
Published: March 2015

Objective

In the presurgical workup of magnetic resonance imaging (MRI)‐negative (MRI− or “nonlesional”) pharmacoresistant focal epilepsy (PFE) patients, discovering a previously undetected lesion can drastically change the evaluation and likely improve surgical outcome. Our study utilizes a voxel‐based MRI postprocessing technique, implemented in a morphometric analysis program (MAP), to facilitate detection of subtle abnormalities in a consecutive cohort of MRI− surgical candidates.

Methods

Included in this retrospective study was a consecutive cohort of 150 MRI− surgical patients. MAP was performed on T1‐weighted MRI, with comparison to a scanner‐specific normal database. Review and analysis of MAP were performed blinded to patients' clinical information. The pertinence of MAP+ areas was confirmed by surgical outcome and pathology.

Results

MAP showed a 43% positive rate, sensitivity of 0.9, and specificity of 0.67. Overall, patients with the MAP+ region completely resected had the best seizure outcomes, followed by the MAP− patients, and patients who had no/partial resection of the MAP+ region had the worst outcome (p < 0.001). Subgroup analysis revealed that visually identified subtle findings are more likely correct if also MAP+. False‐positive rate in 52 normal controls was 2%. Surgical pathology of the resected MAP+ areas contained mainly non–balloon‐cell focal cortical dysplasia (FCD). Multiple MAP+ regions were present in 7% of patients.

Interpretation

MAP can be a practical and valuable tool to: (1) guide the search for subtle MRI abnormalities and (2) confirm visually identified questionable abnormalities in patients with PFE due to suspected FCD. A MAP+ region, when concordant with the patient's electroclinical presentation, should provide a legitimate target for surgical exploration. Ann Neurol 2015;77:1060–1075
Activation of Water in Titanium Dioxide Photocatalysis by Formation of Surface Hydrogen Bonds: An In Situ IR Spectroscopy Study
Authors: Sheng Hua , Zhang Hongna , Song Wenjing , Ji Hongwei , Ma Wanhong , Chen Chuncheng , Zhao Jincai
Published: March 2015

The hole‐driving oxidation of titanium‐coordinated water molecules on the surface of TiO2 is both thermodynamically and kinetically unfavorable. By avoiding the direct coordinative adsorption of water molecules to the surface Ti sites, the water can be activated to realize its oxidation. When TiO2 surface is covered by the H‐bonding acceptor F, the first‐layer water adsorption mode is switched from Ti coordination to a dual H‐bonding adsorption on adjacent surface F sites. Detailed in situ IR spectroscopy and isotope‐labeling studies reveal that the adsorbed water molecules by dual H‐bonding can be oxidized to O2 even in the absence of any electron scavengers. Combined with theoretical calculations, it is proposed that the formation of the dual H‐bonding structure can not only enable the hole transfer to the water molecules thermodynamically, but also facilitate kinetically the cleavage of OH bonds by proton‐coupled electron transfer process during water oxidation.
Synthese BN‐isosterer Verbindungen von Azofarbstoffen durch Ringerweiterung von Borolen mit Aziden
Authors: Braunschweig Holger , Celik Mehmet Ali , Hupp Florian , Krummenacher Ivo , Mailänder Lisa
Published: March 2015

Wir stellen hier die Ergebnisse unserer Untersuchungen bezüglich des Effekts der ortho‐Substitution von Arylaziden auf die Ringerweiterung von Borolen, fünfgliedrigen, ungesättigten Borheterocyclen, vor. Die Studien führten zu der Isolierung der ersten 1,2‐Azaborinin‐substituierten Azofarbstoffe, bei denen es sich um leuchtend gelbe Feststoffe handelt. In Lösung stellte sich eines der Derivate, (E)‐2‐Mesityl‐1‐(mesityldiazenyl)‐3,4,5,6‐tetraphenyl‐1,2‐azaborinin, als nicht stabil heraus, sondern geht eine Jacobsen‐Reaktion zu einem Indazol und einem 1‐Hydro‐1,2‐azaborinin ein. Um den Mechanismus der unerwarteten Bildung der Azo‐Azaborinine nachvollziehen zu können und um Rückschlüsse auf die Rolle der ortho‐Substitution auf den Reaktionsverlauf zu ziehen, wurden Dichtefunktionalrechnungen durchgeführt.
Secondary Crystal Nucleation: Nuclei Breeding Factory Uncovered
Authors: Anwar Jamshed , Khan Shahzeb , Lindfors Lennart
Published: March 2015

Secondary nucleation, wherein crystal seeds are used to induce crystallization, is widely employed in industrial crystallizations. Despite its significance, our understanding of the process, particularly at the molecular level, remains rudimentary. An outstanding question is why do a few seeds give rise to a many‐fold increase in new crystals? Using molecular simulation coupled with experiments we have uncovered the molecular processes that give rise to this autocatalytic behavior. The simulations reveal formation of molecular aggregates in solution, which on coming in contact with the surface of the seed undergo nucleation to form new crystallites. These crystallites are weakly bound to the crystal surface and can be readily sheared by fluid, making the seed surfaces available again to repeat the process. Further, the new crystallites on development can in turn serve as seeds. This mechanistic insight will enable better control in engineering crystalline products to design.
Unprecedented Quassinoids with Promising Biological Activity from Harrisonia perforata
Authors: Fang Xin , Di Ying Tong , Zhang Yu , Xu Zhi Ping , Lu Yang , Chen Qian Qian , Zheng Qi Tai , Hao Xiao Jiang
Published: March 2015

Perforalactone A (1), a new 20S quassinoid with a unique cagelike 2,4‐dioxaadamantane ring system and a migrated side chain, was isolated from the plant Harrisonia perforata together with two biosynthetically related new quassinoids. The structures of these natural products were elucidated by NMR spectroscopy, X‐ray diffraction analysis, computational modeling, and the CD excitation chirality method. The compounds exhibited notable biological properties, including insecticidal activity against Aphis medicaginis Koch and antagonist activity at the nicotinic acetylcholine receptor of Drosophila melanogaster. The structural features of these compounds may be related to their promising biological characteristics. Their biosynthesis and an alternative origin of quassinoid‐type natural products are also discussed.
Superstructure of a Substituted Zeolitic Imidazolate Metal–Organic Framework Determined by Combining Proton Solid‐State NMR Spectroscopy and DFT Calculations
Authors: Baias Maria , Lesage Anne , Aguado Sonia , Canivet Jerome , Moizan‐Basle Virginie , Audebrand Nathalie , Farrusseng David , Emsley Lyndon
Published: March 2015

We report the supercell crystal structure of a ZIF‐8 analog substituted imidazolate metal–organic framework (SIM‐1) obtained by combining solid‐state nuclear magnetic resonance and powder X‐ray diffraction experiments with density functional theory calculations.
KNOCKDOWN OF THE IONOTROPIC γ‐AMINOBUTYRIC ACID RECEPTOR (GABAR) RDL GENE DECREASES FIPRONIL SUSCEPTIBILITY OF THE SMALL BROWN PLANTHOPPER, Laodelphax striatellus (HEMIPTERA: DELPHACIDAE)
Authors: Wei Qi , Wu Shun‐Fan , Niu Chun‐Dong , Yu Hua‐Yang , Dong Yao‐Xue , Gao Cong‐Fen
Published: March 2015

Insect γ‐aminobutyric acid receptors (GABARs) are important molecular targets of cyclodiene and phenylpyrazole insecticides. Previously GABARs encoding rdl (resistant to dieldrin) genes responsible for dieldrin and fipronil resistance were identified in various economically important insect pests. In this study, we cloned the open reading frame cDNA sequence of rdl gene from fipronil‐susceptible and fipronil‐resistant strains of Laodelphax striatellus (Lsrdl). Sequence analysis confirmed the presence of a previously identified resistance‐conferring mutation. Different alternative splicing variants of Lsrdl were noted. Injection of dsLsrdl reduced the mRNA abundance of Lsrdl by 27–82%, and greatly decreased fipronil‐induced mortality of individuals from both susceptible and resistant strains. These data indicate that Lsrdl encodes a functional RDL subunit that mediates susceptibility to fipronil. Additionally, temporal and spatial expression analysis showed that Lsrdl was expressed at higher levels in eggs, fifth‐instar nymphs, and female adults than in third‐instar and fourth‐instar nymphs. Lsrdl was predominantly expressed in the heads of 2‐day‐old female adults. All these results provide useful background knowledge for better understanding of fipronil resistance related ionotropic GABA receptor rdl gene expressed variants and potential functional differences in insects.
Lack of Association of Oral Calcium Supplementation With Coronary Artery Calcification in Rheumatoid Arthritis
Authors: Geraldino‐Pardilla Laura , Dhaduvai Shanthi , Giles Jon T. , Bathon Joan M.
Published: March 2015

Objective

To investigate the association between oral calcium supplementation and coronary artery calcification among rheumatoid arthritis (RA) patients without known cardiovascular disease (CVD).

Methods

This study was conducted as a nested, prospective cohort study of RA patients without known CVD. The daily supplemental calcium dose was ascertained from each patients’ list of prescription and over‐the‐counter medications at baseline and at visit 2 (median 20 months postbaseline). The coronary artery calcium (CAC) score, a measure of coronary atherosclerosis, was assessed by cardiac multidetector row computed tomography at baseline and at visit 3 (median 39 months postbaseline). The association between calcium supplementation and CAC was explored.

Results

Among the 145 RA patients studied, 42 (28%) were taking ≥1,000 mg/day of supplemental calcium at baseline. A CAC score of >100 units was seen in 44 patients (30%) at baseline and 50 patients (34%) at followup. Baseline CAC scores of >100 units were significantly less frequent in patients receiving the higher dosage (≥1,000 mg/day) of supplemental calcium than in those receiving the lower dosage (<1,000 mg/day) (odds ratio [OR] 0.28, 95% confidence interval [95% CI] 0.11–0.74); this association remained significant after adjustment for relevant confounders (adjusted OR 0.30, 95% CI 0.09–0.93). Similarly, at the third study visit, CAC scores of >100 units were less frequent in the higher supplemental calcium dose group compared to the lower dose group (OR 0.41, 95% CI 0.18–0.95); however, after adjustment for relevant confounders, the statistical significance of this association was lost (adjusted OR 0.39, 95% CI 0.14–1.12). No effect of sex heterogeneity was seen in the association of calcium supplementation with coronary artery calcification, and no change in the CAC score over time was observed.

Conclusion

Higher levels of oral calcium supplementation were not associated with an increased risk of coronary atherosclerosis, as measured by the CAC score, in this RA cohort.
Sibling Exposure and Risk of Juvenile Idiopathic Arthritis
Authors: Miller Jessica , Ponsonby Anne‐Louise , Pezic Angela , Kemp Andrew , Piper Susan E. , Akikusa Jonathan D. , Allen Roger C. , Munro Jane E. , Ellis Justine A.
Published: March 2015

Objective

Susceptibility to juvenile idiopathic arthritis (JIA) is presumed to be determined by both genes and environment. However, the environmental factors remain largely unknown. The hygiene hypothesis suggests that exposure to siblings, as a marker of exposure to microbes in early life, may protect against the development of later immune disorders. Some prior evidence suggests this may also be true for JIA. The present study was undertaken to test this hypothesis in detail.

Methods

We conducted a comprehensive analysis of the role of sibling exposure in JIA risk within the Childhood Arthritis Risk Factor Identification Study JIA case–hospital control sample (302 cases and 676 controls) from Victoria, Australia.

Results

We found that, compared to being an only child, having any siblings was protective against JIA, with an adjusted odds ratio (OR) of 0.46 (95% confidence interval [95% CI] 0.28–0.74) (P = 0.001). The protective association appeared to increase with increasing number of siblings (e.g., for ≥3 siblings, adjusted OR 0.25 [95% CI 0.13–0.48], P < 0.001). A protective association of siblings was also observed when we considered cumulative sibling years by age 6 (e.g., for ≥3 years of exposure versus no exposure, adjusted OR 0.49 [95% CI 0.30–0.79], P = 0.003). We also compared cases to a second control sample (n = 341) collected from the community and weighted to represent the child population of Victoria. Data remained supportive of an association between sibling exposure and protection against JIA, particularly for exposure to younger siblings.

Conclusion

Increased exposure to siblings is associated with a reduced risk of disease in our sample. This suggests that increased microbial exposure in childhood may confer protection against the development of JIA.
Adaptive Motion/Force Tracking Control for a Class of Mobile Manipulators
Authors: Sun Wei , Wu Yuqiang
Published: March 2015

In this paper, modeling and adaptive motion/force tracking control is considered for a class of mobile manipulators under the holonomic and affine constraints with the presence of uncertainties and disturbances. Based on a suitable reduced dynamic model, adaptive controllers are proposed to ensure that the states of a closed‐loop system asymptotically track desired trajectories while the constraint force remains bounded by tuning design parameters. Detailed simulation results confirm the effectiveness of the control strategy.
Intertemporal Similarity: Discounting as a Last Resort
Authors: Stevens Jeffrey R.
Published: March 2015

Standard models of intertemporal choice assume that individuals discount future payoffs by integrating reward amounts and time delays to generate a discounted value. Alternative models propose that, rather than integrate across them, individuals compare within attributes (amounts and delays) to determine if differences in one attribute outweigh differences in another attribute. For instance, the similarity model 1) compares the two reward amounts to determine whether they are similar, 2) compares the similarity of the two time delays, and then 3) makes a decision based on these similarity judgments. Here, I tested discounting models against attribute‐based models that use similarity judgments to make choices. I collected intertemporal choices and similarity judgments for the reward amounts and time delays from participants in three experiments. All experiments tested the ability of discounting and similarity models to predict intertemporal choices. Model generalization analyses showed that the best predicting models started with similarity judgments and then, if similarity failed to make a prediction, resorted to discounting models. Similarity judgments also matched intertemporal choice data demonstrating both the magnitude and sign effects, thereby accounting for behavioral data that contradict many discounting models. These results highlight the possibility that attribute‐based models such as the similarity models provide alternatives to discounting that may offer insights into the process of making intertemporal choices. Copyright © 2015 John Wiley & Sons, Ltd.
Comparison of colorimetric and chemiluminescent enzyme‐linked immunosorbent assay for the detection of endosulfan in food samples
Authors: Deepak T. S. , Rashmi Shenoy , Manonmani Haravey K.
Published: March 2015

Pesticides have become part of food protection since their inception. Endosulfan, an organochlorine insecticide, has been used against insect pests such as whiteflies, aphids, red spiders and mites. Methods of immunochemical assays have been devised for the determination and analysis of pesticides and commonly used for the analysis of contaminants in food, water, soil and body fluids. Chicken IgY antibodies raised against endosulfan haptens were used for the detection of endosulfan. We have compared colorimetric (CO) and chemiluminescence (CL) enzyme‐linked immunosorbent assay (ELISA) techniques for the detection of endosulfan isomers in a food matrix. CL ELISA assay was found to be more sensitive than CO assay. The mean recovery was 81.2–95.6% for α‐ and β‐endosulfan‐spiked food samples with 2.8–4.6% relative standard deviation. The detection of the endosulfan isomers was linear in the range 100 µg/mL–5 fg/mL, with a limit of detection at 100 µg/mL and 5 fg/mL for the CL ELISA method and 100 µg/mL and 1 ng/mL for the CO ELISA method respectively. These methods can be used for the rapid and reliable detection of organochlorine pesticide endosulfan. Copyright © 2015 John Wiley & Sons, Ltd.
A very simple high‐performance liquid chromatographic method with fluorescence detection for the determination of gemifloxacin in human breast milk
Authors: Sagirli Olcay , Demirci Seda , Önal Armağan
Published: March 2015

A high‐performance liquid chromatographic method with fluorescence detection was developed and validated for the determination of gemifloxacin in human breast milk. The proposed method allows the determination of gemifloxacin in breast milk samples without complex sample preparation. The samples were mixed with a mobile phase and filtered with a 0.45 µm polytetrafluoroethylene filter before analysis. Chromatographic separation was carried out on a C18 column (150 × 4.6 mm, 5 µm I.D.) using methanol:50 mM ortho‐phosphoric acid solution (40:60) as the mobile phase with a 1.0 mL/min flow rate. Quantitation was performed using fluorescence detection with an excitation wavelength at 272 nm and an emission wavelength at 395 nm. The linear range was found to be 0.1–2.5 µg/mL. The method was applied successfully for the determination of gemifloxacin in breast milk obtained from a breastfeeding mother after oral administration of a single tablet that included 320 mg gemifloxacin per gemifloxacin tablet. Copyright © 2015 John Wiley & Sons, Ltd.
Characterization of the constituents in rat plasma after oral administration of radix polygoni multiflori extracts by ultra‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry
Authors: Lin Longfei , Lin Hongmei , Yin Xingbin , Zhao Yang , Xia Zhenwen , Zhang Miao , Li Xuechun , Han Jing , Qu Changhai , Ni Jian
Published: March 2015

An ultra‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry method was established to detect as many constituents in rat plasma as possible after oral administration of Radix polygoni multiflori (RPM) extract. A C18 column (150 × 2.0 mm, 4 µm) was adopted to separate the samples, and mass spectra were acquired in negative modes. The fingerprints of RPM extract were established, resulting in 39 components being detected. Among these compounds, 29 were identified by comparing the retention times and mass spectral data with those of reference standards and relevant references, and eight compounds were separated and detected in RPM for the first time. In vivo, 23 compounds were observed in dosed rat plasma, 16 of 23 compounds were indicated as prototype components of RPM, and seven compounds were predicted to be metabolites of RPM. A high‐speed and sensitive method was developed and was successfully utilized for screening and characterizing the ingredients and metabolites of RPM. Copyright © 2015 John Wiley & Sons, Ltd.
Determination of corilagin in rat plasma using a liquid chromatography–electrospray ionization tandem mass spectrometric method
Authors: Chen Qian Qian , Guo Jianru , Fan Hongyan , Wang Caiyun , Xu Fengguo , Zhang Wei
Published: March 2015

A sensitive and simple liquid chromatography–tandem mass spectrometric (HPLC‐MS/MS) method for the determination of corilagin in rat plasma has been developed. Samples were prepared with protein precipitation method and analyzed with a triple quadrupole tandem mass spectrometer. We employed negative electrospray ionization as the ionization source and the analytes were detected in multiple reaction monitoring mode. Separation was achieved on a C8 column eluted with mobile phase consisting of methanol–0.1% formic acid in a gradient mode at the flow rate of 0.3 mL/min. The total run time was 7.0 min.This method was proved to have good linearity in the concentration range of 2.5–1000.0 ng/mL. The lower limit of quantification of corilagin was 2.5 ng/mL. The intra‐ and inter‐day relative standard deviationa across three validation runs for four concentration levels were both <9.8%. The relative error was within ±6.0%. This assay offers advantages in terms of expediency and suitability for the analysis of corilagin in rat plasma. The practical utility of this new HPLC‐MS/MS method was confirmed in pilot plasma concentration studies in rats following oral administration. Copyright © 2015 John Wiley & Sons, Ltd.
Structure, Activity and Stereoselectivity of NADPH‐Dependent Oxidoreductases Catalysing the S‐Selective Reduction of the Imine Substrate 2‐Methylpyrroline
Authors: Man Henry , Wells Elizabeth , Hussain Shahed , Leipold Friedemann , Hart Sam , Turkenburg Johan P. , Turner Nicholas J. , Grogan Gideon
Published: March 2015

Oxidoreductases from Streptomyces sp. GF3546 [3546‐IRED], Bacillus cereus BAG3X2 (BcIRED) and Nocardiopsis halophila (NhIRED) each reduce prochiral 2‐methylpyrroline (2MPN) to (S)‐2‐methylpyrrolidine with >95 % ee and also a number of other imine substrates with good selectivity. Structures of BcIRED and NhIRED have helped to identify conserved active site residues within this subgroup of imine reductases that have S selectivity towards 2MPN, including a tyrosine residue that has a possible role in catalysis and superimposes with an aspartate in related enzymes that display R selectivity towards the same substrate. Mutation of this tyrosine residue—Tyr169—in 3546‐IRED to Phe resulted in a mutant of negligible activity. The data together provide structural evidence for the location and significance of the Tyr residue in this group of imine reductases, and permit a comparison of the active sites of enzymes that reduce 2MPN with either R or S selectivity.
5,5′‐Methylenedisalicylic Acid (MDSA) Modulates SarA/MgrA Phosphorylation by Targeting Ser/Thr Phosphatase Stp1
Authors: Zheng Weihao , Liang Yujie , Zhao Hui , Zhang Jianing , Li Zigang
Published: March 2015

SarA (staphylococcal accessory protein A), MgrA (MarR family of global transcriptional regulator A), and SarZ (a paralogue of SarA) play critical roles in modulating the virulence, drug resistance and autolysis of Staphylococcus aureus. Recently, eukaryotic‐like Ser/Thr kinase/phosphatases (Stk1/Stp1) were found to modulate phosphorylation of these transcriptional regulators as well as staphylococcal virulence. Importantly, an stp1‐deficient strain showed significant virulence reduction in mice, indicative of Stp1 as a potential drug target. Here, we report that MDSA, an inhibitor of MgrA, enhances phosphorylation of SarA/MgrA by inhibiting Stp1 in S. aureus. MDSA is a more‐potent inhibitor (IC50=9.68±0.52 μM) of Stp1 than commonly used phosphatase inhibitors. We anticipate that MDSA could be a lead compound to develop new approaches for reducing staph virulence by targeting Stp1.
Estrogen‐mediated signaling is differentially affected by the expression levels of Sfrp1 in mammary epithelial cells
Authors: Gregory Kelly J. , Schneider Sallie S.
Published: March 2015

Estrogen has been implicated in breast cancer risk for a variety of reasons including its role in stimulating mammary cell division. Secreted frizzled‐related proteins (SFRPs) are a family of Wnt signaling antagonists. Loss of Sfrp1 in mice results in focal ductal epithelial hyperplasias and in humans, loss of SFRP1 is associated with early changes in premalignant breast lesions as well as poor overall survival in patients with early stage breast cancer. Considering that SFRP1 expression is further reduced in ER positive breast cancers when compared with ER negative breast cancers, we chose to determine whether loss of Sfrp1 alters ER signaling. Immunohistochemical analysis revealed that loss of Sfrp1 significantly increased the number of PR and BrdU positve cells in the mammary gland. We further demonstrate that down stream actions of ER‐mediated signaling, including cellular proliferation and PR transcription, are elevated in estradiol treated explant cultures derived from Sfrp1−/− mice. Additionally, we show that Control explant cultures treated with estradiol exhibit an increase in the mRNA levels of Sfrp1. Finally, we establish that in human mammary epithelial cells with either SFRP1 knocked down (TERT‐siSFRP1) and rescued SFRP1 expression (MCF7‐SFRP1), estrogen signaling is augmented. Modulation of ER activity appears to be through a mechanism dependent upon Wnt/β‐catenin activity. Taken together, our data suggest an important control mechanism by which estrogen signaling is tempered in normal cells and indicates why loss of SFRP1 in early lesions might be a causal change leading to enhanced estrogen‐mediated proliferation.