bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma physics of magnetic island coalescence during magnetic reconnection
Authors: Zhou Meng , Pang Ye , Deng Xiaohua , Huang Shiyong , Lai Xiangsheng
Published: July 2014

A large‐scale two‐dimensional electromagnetic particle‐in‐cell simulation was employed to study the magnetic island coalescence/merging process during magnetic reconnection with guide field. The merged island after coalescence is characterized by strong core field and plasma density dip at the island center. We found that the core field enhancement is caused by the out‐of‐plane magnetic field pileup, as well as the field line twisting due to Hall effect. There is an in‐plane electric current loop, which is mainly carried by electrons, circumventing the enhanced core field region. Total force points away or tangentially to the surface of density dip within the merged island, which prevents electrons from higher‐density region entering the lower density region between two merging islands. This is contrary to the force in the secondary island, inside which the total force points toward the island center and constrains plasma there. The coalescence process involves a reconnection at the merging sheet between two islands. Electron frozen‐in condition is violated locally along the merging sheet. It is contributed by both the divergence of electron pressure tensor and electron inertial. Energy dissipation is concentrated on the merging line during coalescence, while a train of dynamo (j′ · E′ < 0) and dissipation (j′ · E′ > 0) regions are distributed along the merging sheet after coalescence. Electrons and ions within the density dip at the island center are accelerated antiparallel to the ambient magnetic field, i.e., along the out‐of‐plane direction. The resultant distribution can excite the Buneman instability and two‐streaming instability, which probably account for the electrostatic solitary waves observed by satellite.
Reactive halogens (BrO and OClO) detected in the plume of Soufrière Hills Volcano during an eruption hiatus
Authors: Donovan Amy , Tsanev Vitchko , Oppenheimer Clive , Edmonds Marie
Published: July 2014

Volcanic plumes are sites of dynamic chemistry involving halogen gases. Here we present new data on the relative abundances of SO2, BrO and OClO gases emitted from Soufrière Hills Volcano [SHV). They were collected during an eruptive hiatus but during sustained degassing at this halogen‐rich volcano. By comparison with data from a previous study during an eruptive phase and application of the data and modeling of Villemant et al. (2008), we suggest that, after consideration of errors, either the rate of HBr conversion to BrO is variable, ranging from ∼30% to ∼15%, and/or the relative partitioning of Cl and Br into the gas phase from the melt changes according to eruptive activity. We examine the potential implications of this for fluid‐melt partitioning, and compare our results with data from the experimental literature. Our work contributes toward understanding the controls on the BrO/SO2 ratio for volcano monitoring purposes; the changes in plume chemistry with regard to bromine at the onset of lava extrusion may be large and rapid. OClO was detected in the plume at SHV for the first time. This species has only previously been detected in emissions from Mount Etna (using ground‐based methods) and from Puyehue Cordon Caulle (using satellite‐based methods). No HCHO or NOy species were detected in the spectra.
First modulation of high‐frequency polar mesospheric summer echoes by radio heating of the ionosphere
Authors: Senior A. , Mahmoudian A. , Pinedo H. , La Hoz C. , Rietveld M. T. , Scales W. A. , Kosch M. J.
Published: July 2014

The first high‐frequency (HF, 8 MHz) observations of the modulation of polar mesospheric summer echoes (PMSE) by artificial radio heating of the ionosphere are presented and compared to observations at 224 MHz and model predictions. The experiments were performed at the European Incoherent Scatter facility in northern Norway. It is shown that model results are in qualitative and partial quantitative agreement with the observations, supporting the prediction that with certain ranges of ice particle radii and concentration, PMSE at HF radar wavelengths can be enhanced by heating due to the dominance of dust charging over plasma diffusion.
A hydrologic model demonstrates nitrous oxide emissions depend on streambed morphology
Authors: Marzadri A. , Tonina D. , Bellin A. , Tank J. L.
Published: July 2014

Rivers are hot spots of nitrous oxide (N2O) emissions due to denitrification. Although the key role of rivers in transforming reactive inorganic nitrogen is widely recognized, the recent estimates of N2O emissions by the Intergovernmental Panel on Climate Change (IPCC) may be largely underestimated. This denotes a lack of reliable and robust methodologies to upscale denitrification, and other biogeochemical processes, from the local to the network scale. Here we demonstrate that stream hydromorphology strongly influences N2O emissions. We provide an integrative methodology for upscaling local biogeochemical processes to the catchment scale with a Damköhler number, which accounts for the complex interplay between stream hydromorphology and biogeochemical characteristics of streambed sediments. Application of this theoretical framework to the large data set collected as part of the second Lotic Intersite Nitrogen eXperiment (LINXII) demonstrates that stream morphology is a key factor controlling emissions of N2O from streams.
Characteristics of the O+(2P–2D) 732.0 and 733.0 nm airglow emissions observed with WINDII and simulated with the C‐IAM
Authors: Shepherd Gordon G. , Cho Young‐Min , Fomichev Victor I. , Martynenko Oleg V.
Published: July 2014

This paper provides new data on the O+(2P–2D) 732 nm and 733 nm daytime airglow emissions that enhance our understanding of the role that local and conjugate photoelectrons play in the excitation of this emission, updating earlier investigations of its production by solar EUV photoionization of neutral atomic oxygen. The Wind Imaging Interferometer on the Upper Atmosphere Research Satellite, launched in 1991, retrieved these emissions using a filter primarily intended for observations of the hydroxyl P1(2) line but with invalid results. The first corrected results are presented here and compared with simulations by the Canadian Ionosphere and Atmosphere Model. Reasonable agreement is obtained in terms of vertical profiles, solar flux, and solar zenith angle variations. Observations made during local twilight demonstrate that conjugate photoelectrons do not contribute to the excitation of this emission. This paves the way for future determinations of atomic oxygen concentrations.
Changes in global net radiative imbalance 1985–2012
Authors: Allan Richard P. , Liu Chunlei , Loeb Norman G. , Palmer Matthew D. , Roberts Malcolm , Smith Doug , Vidale Pier‐Luigi
Published: July 2014

Combining satellite data, atmospheric reanalyses, and climate model simulations, variability in the net downward radiative flux imbalance at the top of Earth's atmosphere (N) is reconstructed and linked to recent climate change. Over the 1985–1999 period mean N (0.34 ± 0.67 Wm−2) is lower than for the 2000–2012 period (0.62 ± 0.43 Wm−2, uncertainties at 90% confidence level) despite the slower rate of surface temperature rise since 2000. While the precise magnitude of N remains uncertain, the reconstruction captures interannual variability which is dominated by the eruption of Mount Pinatubo in 1991 and the El Niño Southern Oscillation. Monthly deseasonalized interannual variability in N generated by an ensemble of nine climate model simulations using prescribed sea surface temperature and radiative forcings and from the satellite‐based reconstruction is significantly correlated (r∼0.6) over the 1985–2012 period.
Using MFACE as input in the UAM to specify the MIT dynamics
Authors: Prokhorov B. E. , Förster M. , He M. , Namgaladze A. A. , Holschneider M.
Published: July 2014

The magnetosphere‐ionosphere‐thermosphere (MIT) dynamic system significantly depends on the highly variable solar wind conditions, in particular, on changes of the strength and orientation of the interplanetary magnetic field (IMF). The solar wind and IMF interactions with the magnetosphere drive the MIT system via the magnetospheric field‐aligned currents (FACs). The global modeling helps us to understand the physical background of this complex system. With the present study, we test the recently developed high‐resolution empirical model of field‐aligned currents MFACE (a high‐resolution Model of Field‐Aligned Currents through Empirical orthogonal functions analysis). These FAC distributions were used as input of the time‐dependent, fully self‐consistent global Upper Atmosphere Model (UAM) for different seasons and various solar wind and IMF conditions. The modeling results for neutral mass density and thermospheric wind are directly compared with the CHAMP satellite measurements. In addition, we perform comparisons with the global empirical models: the thermospheric wind model (HWM07) and the atmosphere density model (Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Extended 2000). The theoretical model shows a good agreement with the satellite observations and an improved behavior compared with the empirical models at high latitudes. Using the MFACE model as input parameter of the UAM model, we obtain a realistic distribution of the upper atmosphere parameters for the Northern and Southern Hemispheres during stable IMF orientation as well as during dynamic situations. This variant of the UAM can therefore be used for modeling the MIT system and space weather predictions.
Solar wind control of the terrestrial magnetotail as seen by STEREO
Authors: Opitz Andrea , Sauvaud Jean‐Andre , Klassen Andreas , Gomez‐Herrero Raul , Bucik Radoslav , Kistler Lynn M. , Jacquey Christian , Luhmann Janet , Mason Glenn , Kajdic Primoz , Lavraud Benoit
Published: July 2014

At the beginning of 2007 the twin STEREO spacecraft provided a unique opportunity to study the global solar wind control of the terrestrial magnetotail under typical solar activity minimum conditions. The STEREO‐B (STB) spacecraft flew in the vicinity of the far terrestrial magnetotail, while the STEREO‐A (STA) spacecraft was located in front of the Earth performing measurements in the undisturbed solar wind. In February, the STB spacecraft was located in the magnetosheath most of the time but experienced several incursions into the distant magnetotail. Comparison of STA and STB observations determines unambiguously whether solar wind events such as energetic particle enhancements observed by STB are of pure solar origin or due to the influence of the terrestrial magnetosphere. During this time period in 2007, there were solar minimum conditions with alternating fast and slow solar wind streams that formed corotating interaction regions, which were the dominating source of magnetospheric disturbances encountering the Earth almost every week. Under these conditions, STB experienced multiple bow shock and magnetopause crossings due to the induced highly dynamic behavior of the terrestrial magnetotail and detected bursts of tailward directed energetic ions in the range of 110–2200 keV accompanied by suprathermal electrons of ~700–1500 eV, which were not seen in the undisturbed solar wind by STA. The corotating interaction regions triggered these energetic particle enhancements, and we demonstrate their magnetosphere‐related origin. Even after leaving the magnetosheath in March 2007, STB continued to observe antisunward directed energetic ion bursts until May up to a distance of ~ 800 RE behind Earth, the largest distance to which solar wind and magnetospheric interaction has been observed. These results show that Earth is a very significant source of energetic particles in its local interplanetary environment.
Saffold cardiovirus and multiple sclerosis: no evidence for an association
Authors: Galama Jochem M. D. , Zoll Jan G. , Lanke Kjerstin H. , de Jong Arjan S. , Melief Jeroen , Huitinga Inge , Verbeek Marcel M. , van Kuppeveld Frank J. M.
Published: July 2014

Saffold cardiovirus, a newly discovered human cardiovirus, has close similarity with Theiler's murine encephalomyelitis virus (TMEV) which can cause a chronic demyelinating encephalomyelitis in mice. In this study, we tested whether Saffold cardiovirus infection of the brain is associated with multiple sclerosis (MS). Autopsy white matter samples from 19 MS and 9 normal brain donors were tested by polymerase chain reaction. All were negative. Paired cerebrospinal fluid and serum samples from 24 MS patients and 27 controls were tested for Saffold cardiovirus‐specific oligoclonal bands, two patients and two controls reacted positive. We conclude that an association between Saffold cardiovirus and MS is highly improbable.
Activation Energies Control the Macroscopic Properties of Physically Cross‐Linked Materials
Authors: Appel Eric A. , Forster Rebecca A. , Koutsioubas Alexandros , Toprakcioglu Chris , Scherman Oren A.
Published: July 2014

Here we show the preparation of a series of water‐based physically cross‐linked polymeric materials utilizing cucurbit[8]uril (CB[8]) ternary complexes displaying a range of binding, and therefore cross‐linking, dynamics. We determined that the mechanical strength of these materials is correlated directly with a high energetic barrier for the dissociation of the CB[8] ternary complex cross‐links, whereas facile and rapid self‐healing requires a low energetic barrier to ternary complex association. The versatile CB[8] ternary complex has, therefore, proven to be a powerful asset for improving our understanding of challenging property–structure relationships in supramolecular systems and their associated influence on the bulk behavior of dynamically cross‐linked materials.
Monitoring Morphology and Hydrogen Coverage of Nanometric Pt/γ‐Al2O3 Particles by In Situ HERFD–XANES and Quantum Simulations
Authors: Gorczyca Agnes , Moizan Virginie , Chizallet Celine , Proux Olivier , Del Net William , Lahera Eric , Hazemann Jean‐Louis , Raybaud Pascal , Joly Yves
Published: July 2014

Platinum nanoclusters highly dispersed on γ‐alumina are widely used as heterogeneous catalysts. To understand the chemical interplay between the Pt nanoparticles, the support, and the reductive atmosphere, we performed X‐ray absorption near edge structure (XANES) in situ experiments recorded in high energy resolution fluorescence detection (HERFD) mode. Spectra are assigned by comparison with simulated XANES spectra on models obtained by molecular dynamics (DFT‐MD). We propose platinum cluster morphologies and quantify the hydrogen coverages compatible with XANES spectra recorded at variable hydrogen pressures and temperatures. Using cutting‐edge methodologies to assign XANES spectra, this work gives unequalled atomic insights into the characterization of supported nanoclusters.
Katalytische enantioselektive C‐H‐Funktionalisierung von Alkoholen durch redoxgesteuerte Addition an die Carbonylgruppe: Wasserstoff‐Ausleihe und Kohlenstoff‐Rückgabe
Authors: Ketcham John M. , Shin Inji , Montgomery T. Patrick , Krische Michael J.
Published: July 2014

Die Verwendung von Alkoholen und ungesättigten Reaktanten zur redoxvermittelten Bildung von Nucleophil‐Elektrophil‐Paaren stellt einen breiten, neuartigen Ansatz in der Chemie der Carbonyl‐Addition dar. Mit dieser Vorgehensweise lassen sich diskrete Redoxmanipulationen, die oftmals für die Erzeugung von Carbonyl‐Elektrophilen und vormetallierten Kohlenstoff‐zentrierten Nucleophilen benötigt werden, vermeiden. Die Methode begründet eine neue Klasse von enantioselektiven C‐C‐Kupplungen, die durch Iridium‐ oder Rutheniumkomplexe katalysiert werden.
Polyvinylalkohol als biokompatibles Polymer zur Passivierung von Goldnanostäbchen
Authors: Kinnear Calum , Burnand David , Clift Martin J. D. , Kilbinger Andreas F. M. , Rothen‐Rutishauser Barbara , Petri‐Fink Alke
Published: July 2014

Die Oberflächenfunktionalisierung von Goldnanostäbchen mit Polymeren ist aufgrund der daraus resultierenden kolloidalen Stabilität und der Bioverträglichkeit der Nanopartikel von großer Bedeutung. Die normalerweise vorhandene toxische Doppelschicht aus dem kationische Tensid Cetyltrimethylammoniumbromid (CTAB), das an die Oberfläche der Nanostäbchen adsorbiert ist, erschwert diesen Prozess jedoch erheblich. Nachstehend erläutern wir eine Strategie zur biokompatiblen Funktionalisierung der Nanostäbchen mit hydrophoben Polymervorläufern, hier Polyvinylacetat, die anschließend in ihr hydrophiles Gegenstück, Polyvinylalkohol, überführt werden. Dieses Polymer wurde aufgrund seiner hohen Bioverträglichkeit, den veränderbaren hydrophilen und hydrophoben Eigenschaften und dem hohem Funktionalisierungsgrad gewählt. Die Verträglichkeit der oberflächenfunktionalisierten Goldnanostäbchen wurde an primären Makrophagen, die aus Monozyten differenziert wurden, getestet; die Vorteile der veränderlichen hydrophoben Eigenschaften wurden durch die langfristig stabile Einkapselung eines hydrophoben Beispielmedikaments gezeigt.
Hexacoordinate Nickel(II)/(III) Complexes that Mimic the Catalytic Cycle of Nickel Superoxide Dismutase
Authors: Chatterjee Sudip K. , Maji Ram Chandra , Barman Suman Kumar , Olmstead Marilyn M. , Patra Apurba K.
Published: July 2014

A functional model complex of nickel superoxide dismutase (NiSOD) with a non‐peptide ligand which mimics the full catalytic cycle of NiSOD is unknown. Similarly, it has not been fully elucidated whether NiSOD activity is a result of an outer‐ or inner‐sphere electron‐transfer mechanism. With this in mind, two octahedral nickel(II)/(III) complexes of a bis‐tridentate N2S donor carboxamide ligand, N‐2‐phenylthiophenyl‐2′‐pyridinecarboxamide (HLPh), have been synthesized, structurally characterized, and their SOD activities examined. These complexes mimic the full catalytic cycle of NiSOD. Electrochemical experiments support an outer‐sphere electron‐transfer mechanism for their SOD activity.
Chemoselective Carbophilic Addition of α‐Diazoesters through Ligand‐Controlled Gold Catalysis
Authors: Xi Yumeng , Su Yijin , Yu Zhaoyuan , Dong Boliang , McClain Edward J. , Lan Yu , Shi Xiaodong
Published: July 2014

The chemoselective addition of arenes and 1,3‐diketones to α‐aryldiazoesters was achieved through ligand‐controlled gold catalysis. Unlike a dirhodium catalyst (which promotes CH insertion and cyclopropanation) and a copper catalyst (which catalyzes OH and NH insertions), the gold catalyst with an electron‐deficient phosphite as the ancillary ligand exclusively gave the carbophilic addition product, thus representing a new and efficient approach to form “carbophilic carbocations”, which selectively react with carbon nucleophiles.
Sorption‐Determined Deposition of Platinum on Well‐Defined Platelike WO3
Authors: Wenderich Kasper , Klaassen Aram , Siretanu Igor , Mugele Frieder , Mul Guido
Published: July 2014

The photodeposition of Pt nanoparticles from [PtCl6]2− on platelike WO3 crystals occurs preferentially on the small, subordinate facets. Rather than the often‐used explanation of preferred light‐induced charge migration, we propose that this phenomenon is due to differences in the intrinsic surface charges of WO3 facets exposed to water; thus, the dark sorption of [PtCl6]2− on positively charged facets/edges is preferred. This conclusion is based on 1) (dark) impregnation studies, which showed Pt deposition to also be facet‐specific, and 2) aqueous‐phase AFM studies, which suggest intrinsic surface charges to be in agreement with sorption‐based Pt distributions.
Polyvinyl Alcohol as a Biocompatible Alternative for the Passivation of Gold Nanorods
Authors: Kinnear Calum , Burnand David , Clift Martin J. D. , Kilbinger Andreas F. M. , Rothen‐Rutishauser Barbara , Petri‐Fink Alke
Published: July 2014

The functionalization of gold nanorods (GNRs) with polymers is essential for both their colloidal stability and biocompatibility. However, a bilayer of the toxic cationic surfactant cetyl trimethylammonium bromide (CTAB) adsorbed on the nanorods complicates this process. Herein, we report on a strategy for the biocompatible functionalization of GNRs with a hydrophobic polymeric precursor, polyvinyl acetate, which is then transformed into its hydrophilic analogue, polyvinyl alcohol. This polymer was chosen due to its well‐established biocompatibility, tunable “stealth” properties, tunable hydrophobicity, and high degree of functionality. The biocompatibility of the functionalized GNRs was tested by exposing them to primary human blood monocyte derived macrophages; the advantages of tunable hydrophobicity were demonstrated with the long‐term stable encapsulation of a model hydrophobic drug molecule.
A toughened PLA/Nanosilica composite obtained in the presence of epoxidized soybean oil
Authors: Xiong Zhu , Dai Xinyan , Na Haining , Tang Zhaobin , Zhang Ruoyu , Zhu Jin
Published: July 2014

In this manuscript, a toughened PLA/nanosilica composite with good storage stability was obtained in the presence of the epoxidized soybean oil (ESO). The composite was fabricated via a twin‐screw extruder, and characterized by the FTIR, selective distribution test, and SEM. The surface of nanosilica was modified by the ESO through the chemical bonding, and this rendered the nanosilica to selectively localize in ESO droplets in the composite. As a result, the PLA/nanosilica composite was changed from brittleness to ductility with the addition of ESO. For example, the elongation and notched impact strength of the PLA/silica/ESO nanocomposite with 5 wt % nanosilica and 15 wt % ESO were ∼42% and ∼11 KJ/m2, respectively, which were much higher than neat PLA or PLA/nanosilica composite without ESO. Furthermore, the change of the brittle fracture of PLA into ductile fracture was investigated by SEM micrographs in detail. A possible toughening mechanism was also proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41220.
Fabrication and properties of poly(l‐lactide) nanofibers via blend sea‐island melt spinning
Authors: Zhang Xiuqin , Jin Gaoling , Ma Wenjuan , Meng Lingyan , Yin Huihui , Zhu Zhiguo , Dong Zhenfeng , Wang Rui
Published: July 2014

Poly(l‐lactide) (PLLA) nanofibers were prepared by melt extrusion of immiscible blends of PLLA/low density polyethylene (LDPE) and subsequent removal of the LDPE matrix from the blend fibers. The effect of blends composition and draw ratio on the phase structure of the blend fibers, crystallization, mechanical properties, and the diameter of the PLLA nanofibers was investigated. It is found that the diameter of the PLLA phase gradually increases with the increase of PLLA content. With the variation of PLLA content from 50 to 60 wt %, the average diameter of acquired PLLA nanofibers changes from 119 to 153 nm under the draw ratio of 1.5. When further increasing the content of PLLA to 65%, it is difficult to acquire PLLA nanofibers due to the poor dissolving properties between PLLA and LDPE components. Oriented PLLA nanofibers with the average diameter of 92 nm can be fabricated from PLLA/LDPE (50/50, wt %) blends under the draw ratio of 2. The present results suggest that it is possible to acquire polymer nanofibers with high output using blend sea‐island melt spinning. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41228.
OVARIAN NUTRITIONAL RESOURCES DURING THE REPRODUCTIVE CYCLE OF THE HEMATOPHAGOUSDIPETALOGASTER MAXIMA(HEMIPTERA: REDUVIIDAE): FOCUS ON LIPID METABOLISM
Authors: Leyria Jimena , Fruttero Leonardo L. , Aguirre Silvina A. , Canavoso Lilián E.
Published: July 2014

In this study, we have analyzed the changes of the ovarian nutritional resources inDipetalogaster maximaat representative days of the reproductive cycle: previtellogenesis, vitellogenesis, as well as fasting‐induced early and late atresia. As expected, the amounts of ovarian lipids, proteins, and glycogen increased significantly from previtellogenesis to vitellogenesis and then, diminished during atresia. However, lipids and protein stores found at the atretic stages were higher in comparison to those registered at previtellogenesis. Specific lipid staining of ovarian tissue sections evidenced remarkable changes in the shape, size, and distribution of lipid droplets throughout the reproductive cycle. The role of lipophorin (Lp) as a yolk protein precursor was analyzed by co‐injecting Lp‐OG (where OG is Oregon Green) and Lp‐DiI (where DiI is 1,10‐dioctadecyl‐3,3,30,30‐tetramethylindocarbocyanine) to follow the entire particle, demonstrating that both probes colocalized mainly in the yolk bodies of vitellogenic oocytes. Immunofluorescence assays also showed that Lp was associated to yolk bodies, supporting its endocytic pathway during vitellogenesis. The involvement of Lp in lipid delivery to oocytes was investigated in vivo by co‐injecting fluorescent probes to follow the fate of the entire particle (Lp‐DiI) and its lipid cargo (Lp‐Bodipy‐FA). Lp‐DiI was readily incorporated by vitellogenic oocytes and no lipoprotein uptake was observed in terminal follicles of ovaries at atretic stages. Bodipy‐FA was promptly transferred to vitellogenic oocytes and, to a much lesser extent, to previtellogenic follicles and to oocytes of ovarian tissue at atretic stages. Colocalization of Lp‐DiI and Lp‐Bodipy‐FA inside yolk bodies indicated the relevance of Lp in the buildup of lipid and protein oocyte stores during vitellogenesis.
Thermodriven Micrometer‐Scale Aqueous‐Phase Separation of Amphiphilic Oligoethylene Glycol Analogues
Authors: Kawasaki Shunichi , Muraoka Takahiro , Obara Haruki , Ishii Takerou , Hamada Tsutomu , Kinbara Kazushi
Published: July 2014

Thermoresponsive materials with a lower critical solution temperature (LCST) are receiving growing attention, of which examples of non‐polymeric small molecules are limited. Monodisperse oligoethylene glycol amphiphiles that contain aromatic units with a LCST in water have been developed and applied to peptide extraction. Concentration‐dependent hysteretic transmittance changes were observed in response to temperature elevation and reduction. Dynamic light scattering measurements and phase contrast microscopy revealed the formation of micrometer‐sized aggregates upon heating at a concentration above 5.0 mM; these aggregates self‐assembled to form larger aggregates upon cooling before dissolution. The “interaggregate” interactions are likely to cause the hysteretic behavior. As an application of this thermodriven phase separation, selective extraction of peptide fragments containing high percentages of hydrophobic and aromatic amino acid residues was successfully demonstrated.
Pyrene‐Based Fluorescent Supramolecular Hydrogel: Scaffold for Energy Transfer
Authors: Mukherjee Subrata , Kar Tanmoy , Kumar Das Prasanta
Published: July 2014

The self‐assembled gelation of an amino‐acid‐based low molecular weight gelator having a pyrene moiety at the N terminus and a bis‐ethyleneoxy unit linked with succinic acid at the C terminus is reported. This amphiphile is capable of gelating binary mixtures (1/3 v/v) of CH3CN/water, DMSO/water, and DMF/water, and the minimum gelation concentration (MGC) varied from 0.2 to 0.3 % w/v. The sodium salt of the amphiphile efficiently gelates water with an MGC of 1.5 % w/v. The participation of different noncovalent interactions in supramolecular gelation by formation of fibrillar networks was investigated by spectroscopic and microscopic methods. High mechanical strength of the supramolecular gels is indicated by storage moduli on the order of 103 Pa. The hydrogel was utilized for energy transfer, whereby inclusion of only 0.00075 % w/v of acridine orange resulted in about 50 % quenching of the fluorescence intensity of the gel through fluorescence resonance energy transfer.
Design of H∞ static output feedback control for discrete‐time systems with limited actuator
Authors: Li Yeng‐Fang
Published: July 2014

In this paper, static output feedback (SOF) control analysis and synthesis are conducted for linear discrete‐time systems subject to actuator saturation with an H∞ setting. Typically, the SOF problem is nonconvex; the existence of static output feedback control can be expressed in terms of the solvability of bilinear matrix inequalities (BMIs). Because these BMIs are difficult to solve, they are usually solved by transforming the BMI problem into an iterative linear matrix inequality (ILMI) problem. The actuator saturation problem is also considered since the driving capacity of an actuator is limited in practical applications. Using the classical approach, singular value decomposition (SVD), the H∞ SOF controller design problem for systems with actuator saturation can be expressed in terms of an eigenvalue problem (EVP). The coordination between the minimization of the attenuation level of the H∞ performance and the maximization of the estimation of the region of attraction are considered in our approach in the solution of the proposed EVP. Finally, some numerical examples are given to describe the proposed design procedure.
A New Derivation of the Cubature Kalman Filters
Authors: Zhang Xin‐Chun , Teng Yun‐Long
Published: July 2014

This paper investigates the cubature Kalman filtering (CKF) for nonlinear dynamic systems. This third‐degree rule based filter employs a spherical‐radial cubature rule to numerically compute the integrals encountered in nonlinear filtering problems, thereby removing the requirements of explicitly computing the Jacobians. The cubature rule, however, requires computing the intractable integrals over a high‐dimensional spherical region for multidimensional applications. Moreover, the cubature formula that has been used to construct the spherical cubature formula has some demerits, most notably its inconvenient properties in computation and low estimation accuracy. Aimed at these issues, a general class of CKFs that uses only cubature rules is derived in this paper. It can be shown that the conventional CKF is a special case of the proposed algorithm. The paper also includes higher‐degree CKFs, especially two representative types of the fifth‐degree CKFs. Performance of the proposed algorithms is demonstrated via two target tracking problems. The experimental results, presented herein, illustrate the superior performance of higher‐degree CKFs to conventional nonlinear filters.
Decentralized Output Feedback Protocol for Consensus Control of a Class of Nonlinear Dynamics Networks
Authors: Li Zhenxing , Ji Haibo , Sheng Jie
Published: July 2014

This paper studies the consensus control for multi‐agent systems with nonlinear functions satisfying the sector condition. To achieve consensus, we design a distributed output feedback protocol with an undetermined system matrix, and derive some conditions in terms of linear matrix inequalities (LMIs) to guarantee consensus of all agents' states. Furthermore, by solving three LMIs, the system matrix of the output feedback protocol is designed. Finally, we provide a simulation to show the effectiveness of the proposed consensus protocol.
Adaptive Dual Control of Discrete‐Time Lqg Problems with Unknown‐But‐Bounded Parameter
Authors: Qian Fucai , Huang Jiaoru , Liu Ding , Hu Shaolin
Published: July 2014

The dual control for a class of discrete‐time linear‐quadratic Gaussian (LQG) problems is studied in this paper, where there exist unknown‐but‐bounded parameter uncertainties both in the state equation and the observation equation. It is assumed that the unknown parameter belongs to a known bounded interval. To achieve the adaptive dual control, a subdivision for the continuous bounded interval is used, thus, the computational tractability is ensured. Based on such subdivision, the adaptive dual controller developed can learn a more accurate interval that contains the true value of the unknown parameter with a learning error given in advance. The performance of the controller is illustrated with two examples.
Immunological tools: Engaging students in the use and analysis of flow cytometry and enzyme‐linked immunosorbent assay (ELISA)
Authors: Ott Laura E. , Carson Susan
Published: July 2014

Flow cytometry and enzyme‐linked immunosorbent assay (ELISA) are commonly used techniques associated with clinical and research applications within the immunology and medical fields. The use of these techniques is becoming increasingly valuable in many life science and engineering disciplines as well. Herein, we report the development and evaluation of a novel half‐semester course that focused on introducing undergraduate and graduate students to advance conceptual and technical skills associated with flow cytometry and ELISA, with emphasis on applications, experimental design, and data analysis. This course was offered in the North Carolina State University Biotechnology Program over three semesters and consisted of weekly lectures and laboratories. Students performed and/or analyzed flow cytometry and ELISA in three separate laboratory exercises: (1) identification of transgenic zebrafish hematopoietic cells, (2) analysis of transfection efficiency, and (3) analysis of cytokine production upon lipopolysaccharide stimulation. Student learning outcomes were achieved as demonstrated by multiple means of assessment, including three laboratory reports, a data analysis laboratory practicum, and a cumulative final exam. Further, anonymous student self‐assessment revealed increased student confidence in the knowledge and skill sets defined in the learning outcomes. © 2014 by The International Union of Biochemistry and Molecular Biology, 42(5):382–397, 2014.
Guaiacol peroxidase zymography for the undergraduate laboratory
Authors: Wilkesman Jeff , Castro Diana , Contreras Lellys M. , Kurz Liliana
Published: July 2014

This laboratory exercise presents a novel way to introduce undergraduate students to the specific detection of enzymatic activity by electrophoresis. First, students prepare a crude peroxidase extract and then analyze the homogenate via electrophoresis. Zymography, that is, a SDS‐PAGE method to detect enzyme activity, is used to specifically detect peroxidase activity and furthermore, to analyze the total protein profile. After the assay, students may estimate the apparent molecular mass of the enzyme and discuss its structure. After the 4‐h experiment, students gain knowledge concerning biological sample preparation, gel preparation, electrophoresis, and the importance of specific staining procedures for the detection of enzymatic activity. © 2014 by The International Union of Biochemistry and Molecular Biology, 42(5):420–426, 2014.
A Generalizable DNA‐Catalyzed Approach to Peptide–Nucleic Acid Conjugation
Authors: Chu Chih‐Chi , Wong On Yi , Silverman Scott K.
Published: July 2014

We report DNA catalysts (deoxyribozymes) that join tyrosine‐containing peptides to RNA and DNA in one step and without requiring protecting groups on either the peptide or the nucleic acid. Our previous efforts towards this goal required tethering the peptide to a DNA anchor oligonucleotide. Here, we established direct in vitro selection for deoxyribozymes that use untethered, free peptide substrates. This approach enables imposition of selection pressure via reduced peptide concentration and leads to preparatively useful lower apparent Km values of ∼100 μM peptide. Use of phosphorimidazolide (Imp) rather than triphosphate as the electrophile enables reactivity of either terminus (5′ or 3′) of both RNA and DNA. Our findings establish a generalizable means of joining unprotected peptide to nucleic acid in one step by using DNA catalysts identified by in vitro selection.
Post‐ harvest consideration factors for microRNA research in cellular, tissue, serum and plasma samples
Authors: Chiang Vic Shao‐Chih
Published: July 2014

MicroRNA plays important regulatory roles on the genetic network which provides researchers with valuable novel mechanistic directions and perspectives for applications in a wide variety of fields. Despite pertinent insight gained from messenger RNA, microRNAs possess distinct biochemical properties that emphasize the need for independent research to be conducted that addresses specifically microRNA handling. This review provides a brief summary on the various factors at post‐sample harvesting stages with focus on microRNA from cellular, tissue, plasma and serum samples. It incorporates an up‐to‐date discussion on the isolation methods, quality control, profiling methods and other post‐harvesting factors in microRNA research.
Melanocyte migration is influenced by E‐cadherin‐dependent adhesion of keratinocytes in both two‐ and three‐dimensional in vitro wound models
Authors: Keswell Dheshnie , Kidson Susan H. , Davids Lester M.
Published: July 2014

During wound healing, melanocytes are required to migrate into the wounded area that is still in the process of re‐construction. The role and behaviour of melanocytes during this process is poorly understood, that is, whether melanocyte migration into the wound is keratinocyte‐dependent or not. This paper attempts, through the use of both two‐ and three‐dimensional in vitro models, to understand the role and behaviour of melanocytes during the process of wound healing. In addition, it sheds light on whether keratinocytes influence/contribute toward melanocyte migration and ultimately wound healing. Scratch assays were performed to analyse migration and Western blot analyses measured cellular E‐cadherin expression. Immunohistochemistry was used to analyse the in vivo 3D wound healing effect. Scratch assays performed on co‐cultures of melanocytes and keratinocytes demonstrated that melanocytes actively migrated, with the use of their dendrites, into the scratch ahead of the proliferating keratinocyte sheet. Migration of the melanocyte into the wound bed was accompanied by loss of attachment to keratinocytes at the wound front with concomitant downregulation of E‐cadherin expression as observed through immunocytochemistry. This result suggests that, in vitro, melanocyte migration occurs independently of keratinocytes but that the migration is influenced by keratinocyte E‐cadherin expression. We now demonstrate that melanocyte migration during re‐pigmentation is an active process, and suggest that targeting of mechanisms involved in active melanocyte migration (e.g. the melanocyte dendrite) may enhance the re‐pigmentation process.
Lithium chloride suppresses LPS‐mediated matrix metalloproteinase‐9 expression in macrophages through phosphorylation of GSK‐3β
Authors: Kim Sooho , Bong Naeun , Kim Ok Soo , Jin JunYup , Kim Dong‐Eog , Lee Dong Kun
Published: July 2014

Abnormal degradation of matrix components due to dysregulated expression of matrix metalloproteinase (MMP)‐9 in macrophages has been linked to progression of acute cerebral ischemia and atherosclerosis. We report that lithium chloride (LiCl) or CHIR99021, inhibitors of Wnt signaling pathway, enhance phosphorylation of glycogen synthase kinase‐3beta and suppress lipopolysaccharide‐mediated upregulation of MMP‐9 expression in murine macrophage RAW264.7 cells in a dose‐dependent manner. Suppression of MMP‐9 expression by LiCl or CHIR99021 did not result after inhibition of kinases involved in NFκB or AP‐1 family proteins, but from changes in the activity of histone deacetylases. Beneficial effects on atherosclerosis or cerebral ischemia in animal studies caused by LiCl may be in part explained by the suppression of MMP‐9 gene expression.
Carbon Quantum Dot/Silver Nanoparticle/Polyoxometalate Composites as Photocatalysts for Overall Water Splitting in Visible Light
Authors: Liu Juan , Zhang Hengchao , Tang Di , Zhang Xing , Yan Likai , Han Yuzhi , Huang Hui , Liu Yang , Kang Zhenhui
Published: July 2014

The design of photocatalysts for overall water splitting in visible light remains a huge challenge. Carbon quantum dots (CQDs)/Ag/Ag3PW12O40 nanocomposites have high photocatalytic activities for overall water splitting in visible light without electron acceptors or hole scavengers. In the present system, H2 evolution was performed on Ag particles. O2 evolution appears to be a result of the oxidation of H2O on the valence band of Ag3PW12O40, which is enhanced by promoted electron‐transfer events at hybrid interfaces of the polyoxometalates and CQDs. The synergistic effects of CQDs, Ag, and Ag3PW12O40 enable the design of a water‐splitting catalyst with a remarkably improved efficiency (with an active region of λ<650 nm; apparent quantum yield ≈4.9 % at 480 nm) and operational stability.
A New Combustion Route to Synthesize Mixed Valence Vanadium Oxide Heterojunction Composites as Visible‐Light‐Driven Photocatalysts
Authors: Jiang Baojiang , Peng Xiuxia , Qu Yang , Wang Hong , Tian Chungui , Pan Qingjiang , Li Mingxia , Zhou Wei , Fu Honggang
Published: July 2014

The fabrication of a semiconductor heterojunction photocatalyst is a key aim of the visible light photocatalytic field owing to its central role in the enhancement of photogenerated charge separation and quantum efficiency. Herein, a new mixed valence vanadium oxide composite with the VO2@V6O13 heterojunction is fabricated through the facile and direct combustion of an ethanol solution composed of ammonium metavanadate and diethyl imidazole. XRD and TEM analyses reveal the structural evolution at the interface between VO2 and V6O13, which manipulates the electronic structure of the composites. The composition and chemical state of the composites are obtained by using X‐ray photoelectron spectroscopy. In addition, the detailed energy band structure has been confirmed by the analysis of the UV/Vis absorption spectra and X‐ray photoelectron spectroscopy valence band spectra. The mixed valence vanadium oxides readily narrow their energy gap (1.4–2.5 eV), which enables the efficient utilization of visible light and the improvement in charge separation rate. Thus, the photocatalysts with the VO2@V6O13 heterojunction demonstrate improved photocatalytic activity and structural stability in the degradation of atrazine pesticide under visible light irradiation, which is an effective solution for the problem of remnant pesticides for future agriculture. Furthermore, this facile and straightforward method has promising applications in the fabrication of other heterostructure photocatalysts.
Oxidative Grafting of a Redox‐Molecule‐Based Ionic Liquid onto an Electrode Surface: Anion Exchange within a Layer
Authors: Gómez‐Mingot Maria , Bui‐Thi‐Tuyet Van , GaëlleTrippé‐Allard  , Ghilane Jalal , Randriamahazaka Hyacinthe
Published: July 2014

The surface modification of carbon electrodes using an imidazolium‐based ionic liquid bearing a redox functionality is investigated. Electrochemical oxidation of N‐(2‐aminoethyl)‐N‐(4‐nitrophenylethylimidazolium) bromide onto a glassy carbon electrode leads to the immobilization of nitrophenyl‐imidazolium layers. The presence of this layer is evidenced by following the electrochemical signal of the attached redox moieties. Furthermore, the modified electrode behavior is studied in the presence of redox probes, from which it is concluded that the generated layer is very thin and/or less dense, probably due to the specific arrangement of the positively charged imidazolium. In addition, we investigate the capability of performing anion exchange within the immobilized layer by simple immersion of the electrode in the ionic liquid. X‐ray photoelectron analyses evidence the occurrence of the exchange within the layer and confirm the presence of attached nitrophenyl‐imidazolium.
Revealing the Active Intermediates in the Oxidation of Formic Acid on Au and Pt(111)
Authors: Gao Wang , Song Er Hong , Jiang Qing , Jacob Timo
Published: July 2014

The mechanisms of formic acid (HCOOH) oxidation on Au(111) under gas‐phase and electrochemical conditions was studied by using density functional theory and then compared with the analogous processes on Pt(111). Our results demonstrate that a mechanism involving a single intermediate molecule is preferred on both Au and Pt(111). Furthermore, under gas‐phase conditions, HCOOH oxidation proceeds through the same mechanism (formate pathway) on Au and Pt(111), whereas under electrochemical conditions, it can take place through significantly different mechanisms (formate and/or direct pathways), depending on the applied electrode potential. Our calculations help to rationalize conflicting experimental explanations and are crucial for understanding the mechanism of this fundamental (electro‐)catalytic process.
Chemoselective Phototransformation of CH Bonds on a Polymer Surface through a Photoinduced Cerium Recycling Redox Reaction
Authors: Huang Zhenhua , Wu Zhengfang , Yang Peng , Yang Wantai
Published: July 2014

It is generally accepted that Ce4+ is unable to directly oxidize unreactive alkyl CH bonds without the assistance of adjacent polar groups. Herein, we demonstrate in our newly developed confined photochemical reaction system that this recognized issue may be challenged. As we found, when a thin layer of a CeCl3/HCl aqueous solution was applied to a polymeric substrate and the substrate subjected to UV irradiation, Ce3+ was first photooxidized to form Ce4+ in the presence of H+, and the in situ formed Ce4+ then performs an oxidation reaction on the CH bonds of the polymer surface to form surface‐carbon radicals for radical graft polymerization reactions and functional‐group transformations, while reducing to Ce3+ and releasing H+ in the process. This photoinduced cerium recycling redox (PCRR) reaction behaved as a biomimetic system in an artificial recycling reaction, leading to a sustainable chemical modification strategy for directly transforming alkyl CH bonds on polymer surfaces into small‐molecule groups and polymer brushes. This method is expected to provide a green and economical tool for industrial applications of polymer‐surface modification.
Strong Induced‐Fit Binding of Viologen and Pyridine Derivatives in Adjustable Porphyrin Cavities
Authors: Deutman Alexander B. C. , Smits Jan M. M. , de Gelder René , Elemans Johannes A. A. W. , Nolte Roeland J. M. , Rowan Alan E.
Published: July 2014

The synthesis and binding properties of new porphyrin cage compounds consisting of a rigid diphenylglycoluril part, which is connected via flexible bis(ethyleneoxy) spacers to a (metallo)porphyrin “roof”, are reported. Binding of viologen guests and pyridine ligands in these porphyrin cages are accompanied by significant conformational reorganizations of the hosts. Despite these structural changes, association constants are still very high, revealing that not only receptors that bind guests according to a lock‐and‐key mechanism but also those that bind guests by an induced‐fit mechanism can exhibit strong binding.
Convenient Synthesis of Functionalized Bis‐ureidopyrimidinones Based on Thiol‐yne Reaction
Authors: Peng Hui‐Qing , Sun Cai‐Li , Xu Jiang‐Fei , Niu Li‐Ya , Chen Yu‐Zhe , Wu Li‐Zhu , Tung Chen‐Ho , Yang Qing‐Zheng
Published: July 2014

The preparation of functionalized bis‐ureidopyrimidinones (Bis‐UPy) through the thiol‐yne reaction is described. Various Bis‐UPys with different functional groups were synthesized by using the readily available functionalized alkynes and UPy‐thiol to affirm the simplicity and versatility of the methodology.
New Helical Folds in α‐Peptides with Alternating Chirality
Authors: Sharma Gangavaram V. M. , Venkateshwarlu Gajulapati , Reddy Pothula Purushotham , Kunwar Ajit C.
Published: July 2014

In α‐peptides, the 8/10 helix is theoretically predicted to be energetically unstable and has not been experimentally observed so far. Based on our earlier studies on ‘helical induction’ and ‘hybrid helices’, we have adopted the ‘end‐capping’ strategy to induce the 8/10 helix in α‐peptides by using short α/β‐peptides. Thus, α‐peptides containing a regular string of α‐amino acids with alternating chirality were end capped by α/β‐peptides with 11/9‐helical motifs at the termini. Extensive NMR spectroscopy studies of these peptides revealed the presence of a hitherto unknown 8/10‐helical pattern; the H‐bonds in the shorter pseudorings were rather weak. The approach of using short helical motifs to induce new mixed helices in α‐peptides could provide avenues for more versatile design strategies.