bluuebunny/crossref_metadata_2025 huggingface dataset:
Advances in liquid crystalline conjugated polymers
Authors: Akagi Kazuo
Published: April 2009

We review advances in liquid crystalline (LC) conjugated polymers by focusing on (i) ferroelectric and (ii) photoresponsive LC conjugated polymers. In Part 1, LC polyphenylene derivatives were synthesized through substitution of fluorine‐containing chiral LC groups into side chains. Poly(para‐phenylene) [P1] and poly(meta‐phenylene) [P2] derivatives showed chiral smectic C phases responsible for ferroelectricity. They exhibited quick response to electric field, giving switching times of <1 s between two bistable states. The spontaneous polarization (PS) of P2 remained unchanged even after the electric field became zero, affording the residual polarization (PR) whose value was the same as that of PS. This indicates that P2 has a potential memory function based on FLC nature. In Part 2, poly(para‐phenylenevinylene) [P5] and poly(bithienylene‐phenylene) [P6] derivatives were synthesized by introducing dithienylethene moieties into side chains. Drastic quenching of fluorescence occurred when the photoresponsive moiety changed from an open form to a closed one upon an irradiation of ultraviolet light. The quenched fluorescence was recovered through a photoisomerization from the closed form to the open one. Macroscopically aligned P6 film exhibited a linearly polarized fluorescence with significant anisotropy. Reversible quenching and emitting behavior in anisotropic fluorescence was controlled by the photochemical switching. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2463–2485, 2009
Poly‐(p‐phenylene vinylenes) with pendent 2,4‐difluorophenyl and fluorenyl moieties: Synthesis, characterization, and device performance
Authors: Li Shengbiao , Zhao Ping , Huang Yanqin , Li Tingcheng , Tang Chao , Zhu Rui , Zhao Lei , Fan Quli , Huang Shiqiang , Xu Zushun , Huang Wei
Published: April 2009

To improve efficiency, processability, and stability, three novel poly‐(p‐phenylene vinylenes) (PPVs) derivatives (Pa, Pb, and Pc) with pendent 2,4‐difluorophenyl and fluorenyl moieties were synthesized via Gilch reaction. Their structures were characterized by 1H NMR, 13C NMR, and ELEM. ANAL. Compared with those of PPV and MEH‐PPV, the absolute quantum efficiencies of these polymers showed remarkable improvement (measured at 38.7, 37.2, and 20.3%, respectively), which can be attributed to the presence of twisted multiaryl segments and fluorine atoms. TGA revealed that the inflection temperatures of their thermal decomposition curves were above 400 °C. Double‐layered electroluminescent devices with these polymers as light‐emitting layers [ITO/PEDOT:PSS/Polymer/Ba/Al] showed peak emissions at 493/515, 503, and 600 nm and maximum luminance of 2700, 450, and 4700 cd/m2 for Pa, Pb, and Pc, respectively, with onset voltages of ∼4 V. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2500–2508, 2009
Carbon nanotubes decorated with terpyridine‐ruthenium complexes
Authors: Stefopoulos Andreas A. , Pefkianakis Eleftherios K. , Papagelis Konstantinos , Andreopoulou Aikaterini K. , Kallitsis Joannis K.
Published: April 2009

Surface functionalization of CNTs (SWCNTs or MWCNTs) with dendronized alkoxy terpyridine‐Ru(II)‐terpyridine complexes has been accomplished using either the “grafting to” or the “grafting from” approaches. Different sets of easily processable hybrid metallo‐CNTs composites have been efficiently synthesized bearing either monomeric or polymeric side chain tpy‐Ru(II)‐tpy dicomplexes. Their characterization through TGA, UV‐Vis, and Raman techniques revealed various modification degrees depending on the methodology employed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2551–2559, 2009
Synthesis and characterization of novel PDMS nanocomposites using POSS derivatives as cross‐linking filler
Authors: Baumann Theodore F. , Jones Ticora V. , Wilson Thomas , Saab Andrew P. , Maxwell Robert S.
Published: April 2009

We report the synthesis and characterization of novel elastomeric nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) as both the cross‐linker and filler within a polydimethylsiloxane (PDMS) polymer matrix. These polymer composites were prepared through the reaction of octasilane‐POSS (OS‐POSS) with vinyl‐terminated PDMS chains using hydrosilylation chemistry. In addition, larger super‐POSS cross‐linkers, consisting of two pendant hepta(isobutyl)POSS molecules attached to a central octasilane‐POSS core, were also used in the fabrication of the PDMS composites. The chemical incorporation of these POSS cross‐linkers into the PDMS network was verified by solid‐state 1H magic angle spinning NMR. Based on dynamic mechanical analysis, the PDMS nanocomposites prepared with the octafunctional OS‐POSS cross‐linker exhibited enhanced mechanical properties relative to polymer systems prepared with the tetrafunctional TDSS cross‐linker at equivalent loading levels. The observed improvements in mechanical properties can be attributed to the increased dimensionality of the POSS cross‐linker. The PDMS elastomers synthesized from the larger super‐POSS molecule showed improved mechanical properties relative to both the TDSS and OS‐POSS composites due to the increased volume‐fraction of POSS filler in the polymer matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2589–2596, 2009
Control of molecular aggregation in symmetrically substituted π‐conjugated bulky poly(p‐phenylenevinylene)s and their copolymers
Authors: Resmi R. , Amrutha S. R. , Jayakannan M.
Published: April 2009

A new series of symmetrically substituted bulky PPV‐copolymers based on poly(bis‐2,5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene) (BEH‐PPV) bearing tricyclodecane (TCD) pendants were synthesized to study the effect of chain aggregation in the π‐conjugated polymer backbone. The composition of the copolymers was varied up to 100 mol % and the structures of the copolymer were confirmed by NMR and FTIR. The molecular weights of the copolymers were obtained as Mw = 11,500–1,78,800 depending on the TCD‐incorporation in BEH‐PPV. The origin of the π‐aggregation was investigated using mixture of solvents (polar or nonpolar) or temperature as external stimuli. Absorption, photoluminescence, and time‐resolved fluorescence decay techniques were employed as tools to trace molecular aggregation in solution and solid state. The TCD‐substituted bulky copolymers showed almost twice the enhancement in photoluminescence compared with that of BEH‐PPV. Solvent‐induced aggregation studies of copolymers revealed the existence of strong molecular aggregation in BEH‐PPV compared with that of bulky copolymers. Variable temperature studies further evidence for the reversibility of molecular aggregation on heating/cooling cycles and showed isosbetic points with respect to free and aggregated polymer chains. Time‐resolved fluorescent studies confirmed the existence of free and aggregated π‐conjugated species with a life time of 0.1 to 1.0 ns. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2631–2646, 2009
Studies on sulfonic acid functionalized hollow silica spheres/Nafion® composite proton exchange membranes
Authors: Yuan Junjie , Pu Hongting , Yang Zhenglong
Published: April 2009

In this work, sulfonic acid functionalized hollow silica spheres (SAFHSS)/Nafion® composite membranes were prepared by a recasting procedure. The influences of temperature on water uptake, swelling degree, and proton conductivity of the composite membranes were studied. In comparison with the pure recast Nafion® membrane, it was found that water uptake of composite membranes increased with increasing SAFHSS loading at all temperature studied. The swelling degree of SAFHSS/Nafion® composite membranes with 10∼15 wt % SAFHSS loading was lower than that of the pure recast Nafion® at all temperatures in the study. The proton conductivity of SAFHSS/Nafion® composite membranes was constantly higher than that of the pure recast Nafion® at all temperatures (50∼130 °C). In a range from 50 to 130 °C, the highest conductivity of composite membranes was obtained when 10 wt % SAFHSS was loaded. The maximum conductivity reached 0.1 S cm−1 at 100% relative humidity and 100 °C, even the temperature reached to 130 °C, the conductivity of the composite membranes with 10 wt % SAFHSS was still as high as 4.4 × 10−2 S cm−1 at 100% relative humidity, whereas the conductivity of the pure recast Nafion® was only 2.2 × 10−3 S cm−1. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2647–2655, 2009
High quantum yield photoluminescence of new polyamides containing oligo‐PPV amino derivatives and related oligomers
Authors: Roviello Antonio , Borbone Fabio , Carella Antonio , Diana Rosita , Roviello Giuseppina , Panunzi Barbara , Ambrosio Antonio , Maddalena Pasqualino
Published: April 2009

The synthesis and the chemical physical characterization of new photoluminescent (PL) chromophores and polymers are reported. Chromophores (oligo‐PPV symmetric derivatives ending with amino groups) are strong blue emitters with a PL quantum yield of ∼70% in dioxane solution. They have been used to prepare polyamides by reaction with aliphatic acyl dichlorides in which emitting and non emitting units are alternated. PL properties of the synthesized polyamides have been evaluated in solution and reveal a strong blue emission (PL quantum yield ∼60%), To increase the solubility of these systems, oligomers have been purposely prepared and then characterized. They show a peculiar white emission when excited in DMF solution; to get insight into this interesting behavior, asymmetric monoacetylated chromophores have been prepared as model compounds for the chromophoric end groups of the polyamide chains. The emission spectra of these compounds reveal a broad excimeric yellow emission which is responsible, along with the blue emission of the inner chromophoric units, of the overall white emission of the oligomers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2677–2689, 2009
Synthesis and characterization of side‐chain liquid crystalline polymers bearing cholesterol mesogen
Authors: Ahn Suk‐Kyun , Nguyen Le Long T. , Kasi Rajeswari M.
Published: April 2009

A series of new norbornene carboxylic cholesteryl ester monomers with and without alkyl spacers, NBCh, and NBCh‐n, respectively, were synthesized. New side‐chain liquid crystalline homopolymers, PNBCh and PNBCh‐n, were cleanly prepared using NBCh and NBCh‐n, respectively, with Grubbs 2nd generation catalyst. Molecular and structural characterization of monomers and polymers were carried out by nuclear magnetic resonance, NMR, Fourier transform infrared, FT‐IR, spectroscopy, and gel permeation chromatography, GPC. The thermal and liquid crystalline properties of the homopolymers were investigated by differential scanning calorimetry, DSC, thermogravimetric analysis, TGA, and polarized optical microscopy, POM. Small angle and wide angle X‐ray studies of PNBCh‐n in powder and fiber states not only confirmed the formation of smectic A mesophases, but also established their morphologies. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2690–2701, 2009
Nanostructural modifications of polyamide/MMT hybrids under isothermal and nonisothermal elongational flow
Authors: Garofalo E. , Russo G. M. , Scarfato P. , Incarnato L.
Published: April 2009

The aim of this work is to investigate the effects of elongational flow on the nanoscale arrangement of the silicate inside polyamide‐based nanocomposites. Hybrids, at different loadings of a commercial organoclay, were produced by melt compounding using two polyamide matrices, a nylon‐6, and a copolyamide with similar molecular weight and rheological properties. The elongational flow characterization was performed under both isothermal and nonisothermal conditions by using, respectively, an elongational rheometer (SER) and a fiber‐spinning technique. The extensional rheological response of melt‐compounded nanocomposites, correlated to TEM and X‐ray analyses, was used to probe the nanostructural modifications developed during the uniaxial stretching. The results demonstrated that isothermal and nonisothermal elongational flow can modify the nanomorphology of the nanocomposite hybrids affecting the degree of silicate exfoliation as well as the extent of silicate orientation upon the stretching direction. The entity of structural modifications induced by the stretching were highly dependent on the initial nanomorphological state and on the polymer‐clay affinity. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 981–993, 2009
Viscoelastic properties of nanosilica‐filled epoxy composites investigated by dynamic nanoindentation
Authors: Zhang Yang‐Fei , Bai Shu‐Lin , Li Xiong‐Kui , Zhang Zhong
Published: April 2009

The viscoelastic properties of the epoxy filled with silica nanoparicles have been investigated by dynamic nanoindentation and characterized by the storage modulus and loss tangent. The materials studied are neat epoxy and silica/epoxy composites with silica volume fraction of 1, 3, 6, 10, and 14 vol %, respectively. The silica nanoparticles with an average diameter of 25 nm are found to disperse homogeneously in the epoxy matrix. The effect of the particle content, force frequency, and penetration load on the viscoelastic behavior is studied and discussed. The comparison with traditional testing methods such as tension, bending, and DMTA is made. Besides, theoretical results by using micromechanics models are also obtained and compared with the experimental results. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1030–1038, 2009
Improvement of Surface Characteristics by Electroplating Hard Chromium Coating Post Treated by Nanocrystalline Plasma Electrolytic Carbonitriding
Authors: Mofidi Seyed Haman Hedayat , Aliofkhazraei Mahmood , Rouhaghdam Alireza Sabour , Ghobadi Ehsan , Mohsenian Ehsan
Published: April 2009

Nanocrystalline carbonitrides were performed by pulsed plasma electrolytic carbonitriding on hard chromium coating deposited on AISI 1035 substrate by electroplating. The electroplated samples were connected cathodically to a high‐current pulsed power supply and biased to a negative voltage. The treatment times were 30, 60 and 60 min. A thick compound layer was formed on the surface of Cr coating with microhardness of about 1 200 HV0.15. The nanostructure of the treated layers depends strongly on the applied voltage. The wear resistance of the treated layers depended on process parameters. Overall mechanical properties of treated samples show strong relation to morphology and distribution of complex carbonitride nanocrystallites.
Effect of He/CF4 DBD Operating Parameters on PET Surface Modification
Authors: Jacobs Tinneke , Morent Rino , De Geyter Nathalie , Leys Christophe
Published: April 2009

In this paper, a dielectric barrier discharge (DBD) operated at (sub)atmospheric pressure in a 95/5% He/CF4 mixture is employed to increase the hydrophobicity of a poly(ethylene terephthalate) (PET) film. This paper studies the influence of different operating parameters on the hydrophobic properties of the PET film using contact angle measurements. Results clearly show that the hydrophobicity of the PET film is only enhanced when using large gas flows. Moreover, this work demonstrates that operating pressure and discharge power have a significant influence on the rate of plasma modification as well as on the uniformity of the plasma treatment. Also important to mention is that no ageing effect is observed. As a result, one can conclude that the utilized DBD is an efficient tool to create stable, hydrophobic PET surfaces.
High macrolide resistance inStreptococcus pyogenesstrains isolated from children with pharyngitis in China
Authors: Liu Xiaorong , Shen Xuzhuang , Chang Hesheng , Huang Guoying , Fu Zhou , Zheng Yuejie , Wang Libo , Li Chengrong , Liu Lan , Shen Ying , Yang Yonghong
Published: April 2009

Objectives

To assess the macrolide resistance, phenotype, and genotypic characterization ofStreptococcus pyogenesisolated from Chinese children with pharyngitis.

Methods

Minimal inhibitory concentration (MIC) with nine antibiotics was determined on 188 isolates ofS. pyogenescollected from outpatients with pharyngitis in four children's hospitals in different regions of China in 2007. MICs of penicillin, chloramphenicol, cefradine, levofloxacin, macrolide (erythromycin, clarithromycin, azithromycin,), clindamycin, and tetracycline were determined by the microdilution method. The macrolide resistant phenotypes of isolates were determined through a double‐disk. The macrolide‐resistant genes (mefA,ermB, andermA) were amplified by polymerase chain reaction (PCR).

Results

Over 95% were resistant to macrolides, while 92.0% were resistant to tetracycline. We also found that all isolates were sensitive to penicillin, chloramphenicol, cefradine, and levofloxacin. Among the 173 erythromycin resistant strains, 171 (98.8%) were assigned to the cMLS phenotype, while the remaining 2 (1.2%) were assigned to the iMLS phenotype. Among the 171 cMLS isolates, 168 isolates (98.2%) had theermBgene accounting for 98.2%. Meanwhile, 2 iMLS isolates had theermAgene. Macrolides were highly resistant toermBpositive strains (MIC90 > 256 µg/ml). Neither the M‐phenotype nor themefAgene was detected. Meanwhile, our studies of multiple centers showed that consumption of macrolides from 2000 to 2006 was very high.

Conclusion

The main phenotype is cMLS, and theermBgene code is the main resistance mechanism against macrolides inS. pyogenes. The high rate of macrolide resistance toS. pyogeneswas observed, which may be correlated with the overuse of these antibiotics in China. Pediatr Pulmonol. 2009; 44:436–441. © 2009 Wiley‐Liss, Inc.
Spirometry reference values for Navajo children ages 6–14 years
Authors: Arnall David A. , Kanuho Verdell , Interpreter Christina , Nelson Arnold G , Coast J. Richard , Eisenmann Joey C. , Enright Paul L.
Published: April 2009

Spirometry is the most important tool in diagnosing pulmonary disease and is the most frequently performed pulmonary function test. Since respiratory disease is the single greatest cause for morbidity and mortality on the Navajo Nation, the purpose of this study was to create new age and race‐specific pulmonary nomograms for Navajo children. Five hundred fifty‐eight healthy children, ages 6–14 years, attending Navajo Nation elementary schools in Arizona, were asked to perform spirometry to develop population‐specific and tribe‐specific nomograms for forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), and FEV1 Ratio (FEV1/FVC). Spirometry tests from 284 girls and 274 boys met American Thoracic Society quality control standards. Lung function values, except for FEV1/FVC, all increased with height. The lower limit of the normal range for FEV1/FVC was 80%. The spirometry reference equations from the healthy boys and girls were developed. Height and the natural log of height were significant predictors of FEV1, FVC, and FEF25–75% in the gender‐specific models. The resulting population‐specific spirometry reference equations should be used when testing Navajo children ages 6–14 years. However, the use of the NHANES III spirometry reference equations for Caucasian children may not result in significant misclassification in clinical settings providing that a maximal effort is given by the Navajo child being tested. Pediatr Pulmonol. 2009; 44:489–496. © 2009 Wiley‐Liss, Inc.
Temperature‐induced partially unfolded state of hUBF HMG Box‐5: Conformational and dynamic investigations of the Box‐5 thermal intermediate ensemble
Authors: Liu Zhijun , Zhang Jiahai , Wang Xingsheng , Ding Yanwei , Wu Jihui , Shi Yunyu
Published: April 2009

Human upstream binding factor (hUBF) HMG Box‐5 is a highly conserved protein domain, containing 84 amino acids and belonging to the family of the nonspecific DNA‐binding HMG boxes. Its native structure adopts a twisted L shape, which consists of three α‐helices and two hydrophobic cores: the major wing and the minor wing. In this article, we report a reversible three‐state thermal unfolding equilibrium of hUBF HMG Box‐5, which is investigated by differential scanning calorimetry (DSC), circular dichroism spectroscopy, fluorescence spectroscopy, and NMR spectroscopy. DSC data show that Box‐5 unfolds reversibly in two separate stages. Spectroscopic analyses suggest that different structural elements exhibit noncooperative transitions during the unfolding process and that the major form of the Box‐5 thermal intermediate ensemble at 55°C shows partially unfolded characteristics. Compared with previous thermal stability studies of other boxes, it appears that Box‐5 possesses a more stable major wing and two well separated subdomains. NMR chemical shift index and sequential 1HNi‐1HNi+1 NOE analyses indicate that helices 1 and 2 are native‐like in the thermal intermediate ensemble, while helix 3 is partially unfolded. Detailed NMR relaxation dynamics are compared between the native state and the intermediate ensemble. Our results implicate a fluid helix‐turn‐helix folding model of Box‐5, where helices 1 and 2 potentially form the helix 1‐turn‐helix 2 motif in the intermediate, while helix 3 is consolidated only as two hydrophobic cores form to stabilize the native structure. Proteins 2009. © 2009 Wiley‐Liss, Inc.
Surfactant‐induced deposit structures in relation to the biological efficacy of glyphosate on easy‐ and difficult‐to‐wet weed species
Authors: Kraemer Thorsten , Hunsche Mauricio , Noga Georg
Published: April 2009

BACKGROUND: Typical active ingredient (AI) residue patterns are formed during droplet drying on plant surfaces owing to the interaction of spray solution characteristics and leaf micromorphology. Currently, comparatively little is known about the influence of AI deposit patterns within a spray droplet residue area on the penetration and biological efficacy of glyphosate. A scanning electron microscope with energy dispersive X‐ray microanalysis has been used to characterise residue patterns and to quantify the area ultimately covered by glyphosate within the droplet spread area.

RESULTS: The easy‐to‐wet weed species Stellaria media L. and Viola arvensis L., as well as the difficult‐to‐wet Chenopodium album L. and Setaria viridis L., differing in their surface micromorphology, have been used. Rapeseed oil ethoxylates (RSO 5 or RSO 60) were added to glyphosate solutions to provide different droplet spread areas. Addition of RSO 5 enhanced droplet spread area more than RSO 60, and both caused distinct glyphosate residue patterns. The biological efficacy of treatment solutions showed no significant correlation with the area ultimately covered by glyphosate.

CONCLUSION: The results have implications on herbicide uptake models. This study shows that droplet spread area does not correspond to the area ultimately covered by glyphosate, and that the latter does not affect glyphosate phytotoxicity. Copyright © 2009 Society of Chemical Industry
Mixture effects on the glow peak temperature of europium doped binary crystals
Authors: Rodríguez‐Mijangos R. , Perez‐Salas R.
Published: April 2009

Thermoluminescence measurements of beta‐irradiated divalent Europium doped binary divalent alkali halides with RbCl and KBr components at several compositions x have been obtained. A characteristic thermoluminescence glow peak for each concentration is identified and its temperature, varying from 373 to 458 K, is seen to be dependent on composition. The temperature shift is analyzed as an ion size effect. It is stronger when the halogen ions are interchanged, resembling that the recombination of a halogen vacancy with a hole is the principal source of the thermoluminescence glow peaks. The arguments above are used to predict in a gross manner the temperature of the principal thermoluminiscence glow peaks in different halogen families. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication of Bi2O3‐GeO2 glass phosphor co‐doped with Yb3+, Nd3+ for optical coherence tomography light source
Authors: Sakano A. , Mizutani R. , Fuchi S. , Takeda Y.
Published: April 2009

We have investigated spectroscopic properties of Bi2O3‐GeO2 glass co‐doped with Yb3+ and Nd3+ to find appropriate phosphors for an optical coherence tomography (OCT) light source. We have successfully obtained a Gaussian‐like shaped spectrum from 6.0 Yb2O3–5.0 Nd2O3–44.0 Bi2O3–44.0 GeO2–1.0 Sb2O3 (in nominal molar composition) with a full width at half maximum (FWHM) of 91 nm in the wavelength region near 1000 nm. We achieved the luminescence efficiency of 1.4% using a green LED. The interference signal was studied by using a Michelson interferometer. As a result, the coherent length of 5.7 μm was achieved. This value indicates that the depth resolution of the OCT with this light source is twice compared with that of conventional SLDs. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of stimulated Raman pumping toward the first study of chemical reaction dynamics of the muonium atom with H2*
Authors: Sukhorukov Oleksandr , Bakule Pavel , Matsuda Yasuyuki , Kamal Saeid , Momose Takamasa , Fleming Donald
Published: April 2009

The chemical reaction of interest, from the field of μSR spectroscopy, is that of the muonium atom (Mu) with molecular hydrogen in its first vibrational excited state. The stimulated Raman pumping (SRP) technique has been used to prepare H2 in its ν = 1 state in a series of off‐line experiments at the LASIR Lab at UBC. Three different SRP excitation schemes employing the second harmonic of a Nd:YAG laser have been analysed in connection with this application, for 5.5, 13, and 26 cm‐long reaction cells. The laser energy varied from ∼80 to ∼550 mJ/pulse (or from ∼0.07 GW/cm2 to ∼0.46 GW/cm2) at a 10 Hz repetition rate. The importance of injection seeding of the Nd:YAG laser for efficient molecular excitation is shown. The major challenge of this experiment was to ensure a homogeneous excitation over a large volume (few cm3) while achieving a high amount of vibrationally excited H2 (3‐15 Torr). This is demanded by the requirements of superposition of a pulsed muon beam with the laser beam and the expected rate constant of the Mu + H2*(ν=1) →MuH + H reaction. In this endeavour it was also of interest to explore the effect of added moderator gas to the hydrogen and so the effect of Ar/Xe moderator on the efficiency of hydrogen pumping for different SRP excitation schemes is also shown. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical characterization of pseudo‐ordered nanostructured thin films
Authors: Taschuk M. T. , Chai J. , Buriak J. M. , Brett M. J.
Published: April 2009

We have demonstrated the use of tetrahydrofuran (THF) annealed self‐assembled monolayers of polystyrene‐b ‐poly(2‐vinylpyridine) diblock copolymer to produce hexagonal close packed metallic nanoarrays which may be used as substrates to produce ordered nanostructured optical thin films using glancing‐angle deposition. Our film connects the sites of a face‐centered cubic lattice using a triangular spiral deposited on the block copolymer seeds. The optical properties of unseeded and seeded triangular spiral thin films are characterized. While the nanostructured thin films can inherit the periodicity of the underlying seeds, the optical performance is less than that of an unseeded film. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selective formation of dequenched aggregates of rhodamines: comparison with J‐ and H‐aggregates
Authors: Tomioka Akihiro , Kamiyama Yasushi , Fujimoto Atsushi , Kawakami Shin'ya
Published: April 2009

Self‐organized rhodamine aggregates prepared by wetting / dewetting process of an ethanol solution on a hydrophilic glass surface consistently exhibited fluorescence without quenching. Upon annealing, the aggregates exhibited an irreversible transition to quenched state, similar to H‐aggregate, whereas the fluorescence spectrum was unchanged. The as grown highly fluorescent aggregate is a novel aggregate, neither a J‐aggregate nor an H‐aggregate, showing a blue‐shifted excitation spectrum whereas the emission spectrum is similar to that of molecularly dispersed solution. This fluorescent aggregate was only realized in nonequilibrium by the rapid dewetting process. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conservative cascade interpolation on the sphere: An intercomparison of various non‐oscillatory reconstructions
Authors: Norman Matthew R. , Semazzi Fredrick H. M. , Nair Ramachandran D.
Published: April 2009

Various new polynomial and non‐polynomial approximations to a subgrid distribution have been adapted for use in the conservative cascade scheme (CCS) and applied to conservative grid‐to‐grid interpolation on a latitude‐‐longitude grid. These approximations include the following: piecewise parabolic method (PPM), piecewise hyperbolic method (PHM), piecewise double hyperbolic method (PDHM), power‐limited piecewise parabolic method (P‐PPM), piecewise rational method (PRM), third‐order weighted essentially non‐oscillatory (WENO23), fifth‐order weighted essentially non‐oscillatory (WENO35), and a modified piecewise parabolic method (M‐PPM). A series of test cases are performed in which initial gridded data are interpolated between T42 and 2° grids and compared against analytical values. Four initial data profiles are used: smooth harmonic, high‐frequency harmonic, quasi‐polar vortex data and slotted cylinder data. In general, PDHM (WENO35) had the lowest error norms of the three‐(five‐)cell stencil methods. Quite often, M‐PPM gave accuracy comparable to WENO35 at significantly lower cost. Monotonicity violations generally only occurred when interpolating to a finer grid with a maximum violation of 1.8% of the data range. Copyright © 2009 Royal Meteorological Society
An evaluation of the long‐wave radiative transfer code used in the Met Office Unified Model
Authors: Goldblatt C. , Lenton T. M. , Watson A. J.
Published: April 2009

A detailed evaluation of the radiative transfer code used in the Met Office Unified Climate/Forecast Model is performed, comparing it with a line‐by‐line model and testing the climatic effects of errors in a radiative‐‐convective model. The radiative forcing at the tropopause due to CO2 changes within SRES scenarios and across Quaternary glacial cycles is represented with reasonable accuracy, suggesting that surface temperature will be correctly predicted. However, this is achieved by partial cancellation of opposing errors in upward and downward fluxes. The changes in the vertical profiles of radiative fluxes and the changes to surface and top‐of‐atmosphere fluxes all show significant errors, even at twice pre‐industrial CO2. This causes a sign error in the change in the convective flux in the radiative‐‐convective model. Performance of the code deteriorates rapidly above four times pre‐industrial CO2. For less‐abundant greenhouse gases, CH4 and N2O, the errors are larger as a proportion of their radiative forcings. Errors for surface and top‐of‐atmosphere fluxes for CO2 are similar to those from the mean of the general circulation model (GCM) codes submitted to the intercomparison of radiation codes for IPCC AR4, implying that errors as found here may not be uncommon in climate models. A renewed emphasis on accuracy in radiative transfer calculations and openness in intercomparison studies is necessary to improve the modelling of climate change. Copyright © 2009 Royal Meteorological Society
A Gill–Matsuno‐type mechanism explains the tropical Atlantic influence on African and Indian monsoon rainfall
Authors: Kucharski F. , Bracco A. , Yoo J. H. , Tompkins A. M. , Feudale L. , Ruti P. , Dell'Aquila A.
Published: April 2009

Recent studies using coupled atmosphere–ocean models have shown that the tropical Atlantic has a significant impact on the Indian monsoon. In this article, the observational basis for this teleconnection is examined and the physical mechanism responsible for bridging sea‐surface temperatures (SSTs) in the Atlantic and precipitation over India is investigated with idealized atmospheric general circulation model (AGCM) experiments in which constant SST anomalies are prescribed and ‘switched on’ in the tropical Atlantic region. A simple Gill–Matsuno‐type quadrupole response is proposed to explain the teleconnection between the tropical Atlantic and the Indian basin, with an enforcement of the eastward response likely due to nonlinear interactions with the mean monsoon circulation. The simplicity of this mechanism suggests the reproducibility of this result with a broad range of AGCMs. Copyright © 2009 Royal Meteorological Society
Vertical velocity variance and skewness in clear and cloud‐topped boundary layers as revealed by Doppler lidar
Authors: Hogan Robin J. , Grant Alan L. M. , Illingworth Anthony J. , Pearson Guy N. , O'Connor Ewan J.
Published: April 2009

In this paper, observations by a ground‐based vertically pointing Doppler lidar and sonic anemometer are used to investigate the diurnal evolution of boundary‐layer turbulence in cloudless, cumulus and stratocumulus conditions. When turbulence is driven primarily by surface heating, such as in cloudless and cumulus‐topped boundary layers, both the vertical velocity variance and skewness follow similar profiles, on average, to previous observational studies of turbulence in convective conditions, with a peak skewness of around 0.8 in the upper third of the mixed layer. When the turbulence is driven primarily by cloud‐top radiative cooling, such as in the presence of nocturnal stratocumulus, it is found that the skewness is inverted in both sign and height: its minimum value of around −0.9 occurs in the lower third of the mixed layer. The profile of variance is consistent with a cloud‐top cooling rate of around 30 W m−2. This is also consistent with the evolution of the thermodynamic profile and the rate of growth of the mixed layer into the stable nocturnal boundary layer from above. In conditions where surface heating occurs simultaneously with cloud‐top cooling, the skewness is found to be useful for diagnosing the source of the turbulence, suggesting that long‐term Doppler lidar observations would be valuable for evaluating boundary‐layer parametrization schemes. Copyright © 2009 Royal Meteorological Society
Life cycle of the QBO‐modulated 11‐year solar cycle signals in the Northern Hemispheric winter
Authors: Lu Hua , Gray Lesley J. , Baldwin Mark P. , Jarvis Martin J.
Published: April 2009

This paper provides some insights on the quasi‐biennial oscillation (QBO) modulated 11‐year solar cycle (11‐yr SC) signals in Northern Hemisphere (NH) winter temperature and zonal wind. Daily ERA‐40 Reanalysis and ECMWF Operational data for the period of 1958–2006 were used to examine the seasonal evolution of the QBO‐solar cycle relationship at various pressure levels up to the stratopause. The results show that the solar signals in the NH winter extratropics are indeed QBO‐phase dependent, moving poleward and downward as winter progresses with a faster descent rate under westerly QBO than under easterly QBO. In the stratosphere, the signals are highly significant in late January to early March and have a life span of ∼30–50 days. Under westerly QBO, the stratospheric solar signals clearly lead and connect to those in the troposphere in late March and early April where they have a life span of ∼10 days. As the structure changes considerably from the upper stratosphere to the lower troposphere, the exact month when the maximum solar signals occur depends largely on the altitude chosen.

For the low‐latitude stratosphere, our analysis supports a vertical double‐peaked structure of positive signature of the 11‐yr SC in temperature, and demonstrates that this structure is further modulated by the QBO. These solar signals have a longer life span (∼3–4 months) in comparison to those in the extratropics. The solar signals in the lower stratosphere are stronger in early winter but weaker in late winter, while the reverse holds in the upper stratosphere. Copyright © 2009 Royal Meteorological Society
Delocalization in valence bond—Hyperconjugation
Authors: Havenith R. W. A. , van Lenthe J. H.
Published: April 2009

We consider delocalization in small molecules. The valence bond technology allows an arbitrary division of the 1‐electron space in strictly separate, but nonorthogonal, spaces. Allowing or obstructing orbital mixing between subspaces during the SCF procedure is associated with incorporating or eliminating the hyperconjugation effect. We show an example for tert‐butyl and trimethylsilyl cations and radicals. For H2, for which really extensive basis sets are feasible, we extend the basis so far that the delocalization or hyperconjugation effect has nearly disappeared. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Study of the discontinuity of the exchange‐correlation potential in an exactly soluble case
Authors: Gori‐Giorgi Paola , Savin Andreas
Published: April 2009

It was found by Perdew et al. (Phys Rev Lett, 1982, 49, 1691) and by Sham and Schlüter (Phys Rev Lett. 1983, 51, 1884) that the exact Kohn–Sham exchange‐correlation potential of an open system may jump discontinuously as the particle number crosses an integer, with important physical consequences. Recently, Sagvolden and Perdew (Phys Rev A 2008, 77, 012517) have analyzed the discontinuity of the exchange‐correlation potential as the particle number crosses one, with an illustration that uses a model density for the H− ion. In this work, we extend their analysis to the case in which the external potential is the simple harmonic confinement, choosing spring‐constant values for which the two‐electron hamiltonian has an analytic solution. This way, we can obtain the exact, analytic, exchange and correlation potentials for particle number fluctuating between zero and two, illustrating the discontinuity as the particle number crosses one without introducing any model or approximation. We also discuss exchange and correlation separately. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Geometrically faithful homeomorphisms between the electron density and the bare nuclear potential
Authors: Popelier Paul L. A. , Brémond Éric A. G.
Published: April 2009

The topology of the nuclear potential,Vnuc(r), of just over 130 molecules and molecular complexes is investigated and compared with the topology of the electron density ρ(r). As nuclear positions are kept fixed in this comparison, this work screens forgeometrically faithfulhomeomorphisms between ρ(r) andVnuc(r). In this set of molecules spanning simple inorganic moieties, strained (and cyclic) hydrocarbons, (fused) aromatics, boranes, van der Waals complexes, water clusters, and a few biomolecules, about 70% of the systems show this homeomorphism. A simple analytical formula is derived, expressing the position of a (3,−1) critical point in any diatomic as a function of the participating atomic numbers. The topology ofVnuc(r) at one location of a molecule can sensitively depend on the presence or absence of a substituent far away from this location. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Coverage path planning algorithms for agricultural field machines
Authors: Oksanen Timo , Visala Arto
Published: April 2009

In this article, a coverage path planning problem is discussed in the case of agricultural fields and agricultural machines. Methods and algorithms to solve this problem are developed. These algorithms are applicable to both robots and human‐driven machines. The necessary condition is to cover the whole field, and the goal is to find as efficient a route as possible. As yet, there is no universal algorithm or method capable of solving the problem in all cases. Two new approaches to solve the coverage path planning problem in the case of agricultural fields and agricultural machines are presented for consideration. Both of them are greedy algorithms. In the first algorithm the view is from on top of the field, and the goal is to split a single field plot into subfields that are simple to drive or operate. This algorithm utilizes a trapezoidal decomposition algorithm, and a search is developed of the best driving direction and selection of subfields. This article also presents other practical aspects that are taken into account, such as underdrainage and laying headlands. The second algorithm is also an incremental algorithm, but the path is planned on the basis of the machine's current state and the search is on the next swath instead of the next subfield. There are advantages and disadvantages with both algorithms, neither of them solving the problem of coverage path planning problem optimally. Nevertheless, the developed algorithms are remarkable steps toward finding a way to solve the coverage path planning problem with nonomnidirectional vehicles and taking into consideration agricultural aspects. © 2009 Wiley Periodicals, Inc.
Bayesian pharmacovigilance signal detection methods revisited in a multiple comparison setting
Authors: Ahmed Ismaïl , Haramburu Françoise , Fourrier‐Réglat Annie , Thiessard Frantz , Kreft‐Jais Carmen , Miremont‐Salamé Ghada , Bégaud Bernard , Tubert‐Bitter Pascale
Published: April 2009

Pharmacovigilance spontaneous reporting systems are primarily devoted to early detection of the adverse reactions of marketed drugs. They maintain large spontaneous reporting databases (SRD) for which several automatic signalling methods have been developed. A common limitation of these methods lies in the fact that they do not provide an auto‐evaluation of the generated signals so that thresholds of alerts are arbitrarily chosen. In this paper, we propose to revisit the Gamma Poisson Shrinkage (GPS) model and the Bayesian Confidence Propagation Neural Network (BCPNN) model in the Bayesian general decision framework. This results in a new signal ranking procedure based on the posterior probability of null hypothesis of interest and makes it possible to derive with a non‐mixture modelling approach Bayesian estimators of the false discovery rate (FDR), false negative rate, sensitivity and specificity. An original data generation process that can be suited to the features of the SRD under scrutiny is proposed and applied to the French SRD to perform a large simulation study. Results indicate better performances according to the FDR for the proposed ranking procedure in comparison with the current ones for the GPS model. They also reveal identical performances according to the four operating characteristics for the proposed ranking procedure with the BCPNN and GPS models but better estimates when using the GPS model. Finally, the proposed procedure is applied to the French data. Copyright © 2009 John Wiley & Sons, Ltd.
Electrospray Encapsulation of Hydrophilic and Hydrophobic Drugs in Poly(L‐lactic acid) Nanoparticles
Authors: Valo Hanna , Peltonen Leena , Vehviläinen Satu , Karjalainen Milja , Kostiainen Risto , Laaksonen Timo , Hirvonen Jouni
Published: April 2009

An electrospray method is developed for preparation of beclomethasone‐dipropionate‐ and salbutamol‐sulfate‐loaded biodegradable poly(L‐lactic acid) nanoparticles. Different set‐up parameters for electrospraying are examined on particle size, and preparation conditions are optimized for producing spherical‐drug‐loaded nanoscale particles by controllable processing parameters. Polylactide (PLA)–drug nanoparticles with average diameters of around 200 nm are achieved in a stable cone‐jet mode with a flow rate of 4 µL min−1, polymer concentration of 1%, and ammonium hydroxide content of 0.05%. Morphology and size of the drug–polymer nanoparticles are analyzed by scanning electron microscopy and transmission electron microscopy. Changes in the crystallinity of the PLA polymer and the model drugs are detected by X‐ray powder diffraction, and the absence of molecular interactions are confirmed by thermal analyses. The results indicate clearly that electrospraying is a potential method for producing polymeric nanoparticles and for encapsulating both hydrophilic and hydrophobic drugs efficiently into the nanoparticles.
Designing Nanogadgetry for Nanoelectronic Devices with Nitrogen‐Doped Capped Carbon Nanotubes
Authors: Lee Sang Uck , Belosludov Rodion V. , Mizuseki Hiroshi , Kawazoe Yoshiyuki
Published: April 2009

A systematic analysis of electron transport characteristics for 1D heterojunctions with two nitrogen‐doped (N‐doped) capped carbon nanotubes (CNTs) facing one another at different conformations is presented considering the chirality of CNTs (armchair(5,5) and zigzag(9,0)) and spatial arrangement of N‐dopants. The results show that the modification of the molecular orbitals by the N‐dopants generates a conducting channel in the designed CNT junctions, inducing a negative differential resistance (NDR) behavior, which is a characteristic feature of the Esaki‐like diode, that is, tunneling diode. The NDR behavior significantly depends on the N‐doping site and the facing conformations of the N‐doped capped CNT junctions. Furthermore, a clear interpretation is presented for the NDR behavior by a rigid shift model of the HOMO‐ and LUMO‐filtered energy levels in the left and right electrodes under the applied biases. These results give an insight into the design and implementation of various electronic logic functions based on CNTs for applications in the field of nanoelectronics.
Photoconductivity of Bulk‐Film‐Based Graphene Sheets
Authors: Lv Xin , Huang Yi , Liu Zhibo , Tian Jianguo , Wang Yan , Ma Yanfeng , Liang Jiajie , Fu Shipeng , Wan Xiangjian , Chen Yongsheng
Published: April 2009

Time‐resolved photoconductivity measurements are carried out on graphene films prepared by using soluble graphene oxide. High photocurrent generation efficiency is observed for these graphene‐based films, and the relationships between their photoconductivity and different preparation methods, incident light intensity, external electric field, and photon energies are investigated. Higher photoconductivity is observed with higher photon energy at same incident light intensity. By fitting the experimental data to the Onsager model, the primary quantum yields for charge separation to generate bound electron–hole pairs and the initial ion‐pair thermalization separation distance are calculated.
DNER, an Epigenetically Modulated Gene, Regulates Glioblastoma-Derived Neurosphere Cell Differentiation and Tumor Propagation
Authors: Sun Peng , Xia Shuli , Lal Bachchu , Eberhart Charles G. , Quinones-Hinojosa Alfredo , Maciaczyk Jarek , Matsui William , DiMeco Francesco , Piccirillo Sara M. , Vescovi Angelo L. , Laterra John
Published: April 2009

Neurospheres derived from glioblastoma (GBM) and other solid malignancies contain neoplastic stem-like cells that efficiently propagate tumor growth and resist cytotoxic therapeutics. The primary objective of this study was to use histone-modifying agents to elucidate mechanisms by which the phenotype and tumor-promoting capacity of GBM-derived neoplastic stem-like cells are regulated. Using established GBM-derived neurosphere lines and low passage primary GBM-derived neurospheres, we show that histone deacetylase (HDAC) inhibitors inhibit growth, induce differentiation, and induce apoptosis of neoplastic neurosphere cells. A specific gene product induced by HDAC inhibition, Delta/Notch-like epidermal growth factor-related receptor (DNER), inhibited the growth of GBM-derived neurospheres, induced their differentiation in vivo and in vitro, and inhibited their engraftment and growth as tumor xenografts. The differentiating and tumor suppressive effects of DNER, a noncanonical Notch ligand, contrast with the previously established tumor-promoting effects of canonical Notch signaling in brain cancer stem-like cells. Our findings are the first to implicate noncanonical Notch signaling in the regulation of neoplastic stem-like cells and suggest novel neoplastic stem cell targeting treatment strategies for GBM and potentially other solid malignancies.

Disclosure of potential conflicts of interest is found at the end of this article.