bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and study of novel polyol‐bound photosensitizers for cationic UV‐curable systems
Authors: Chen Zhigang , Webster Dean C.
Published: June 2006

Novel cationic intramolecular hydrogen abstraction photosensitizers (IHA‐PSs) based on a proposed intramolecular hydrogen abstraction photosensitization (IHAP) mechanism were synthesized and found to have a pronounced photosensitization effect in cycloaliphatic epoxide based cationic UV‐curable systems using sulfonium salt photoinitiators. A series of polyol‐based photosensitizers were synthesized with naphthalene attached. One photosensitizer, P‐Na, was found to have a more pronounced photosensitization effect in three different formulation systems, as revealed by real‐time Fourier transform infrared and differential photocalorimetry experiments. Such a phenomenon can be explained by a proposed facile IHAP mechanism, which is possible only with the unique molecular structure of P‐Na. The effect of P‐Na was further confirmed by comparison with two non‐polyol‐type photosensitizers. A designed IHA‐PS molecule was synthesized with the proposed principles ofthe IHAP mechanism, and it achieved a photosensitization effect similar to that of P‐Na with a much lower molecular weight and fewer hydroxyl groups per molecule. This further validated the proposed IHAP mechanism. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4435–4449, 2006
Influence of hexadecane on the formation of droplets and growth of particles for methyl methacrylate miniemulsion polymerization
Authors: Jeng Jauder , Dai Chi‐An , Chiu Wen‐Yen , Chern Chorng‐Shyan , Lin King‐Fu , Young Pin‐Yen
Published: June 2006

The evolution of monomer droplets and latex particles of methyl methacrylate miniemulsions, initiated by an oil‐phase initiator, stabilized by a cationic surfactant mixture, and costabilized by different amounts of hexadecane, was investigated. With an increasing hexadecane concentration, the ultrasonication time required for the miniemulsions to reach a critically stabilized state was reduced, and a unimodal size distribution of the droplets with a decreasing average diameter was obtained. For lower hexadecane concentrations, a bimodal size distribution of the latex particles, with a significant increase in the volume fraction of the smaller latex particles, was achieved after the polymerization. The enhanced growth of the volume fraction of the smaller latex particles came from both nucleation of the shrinking droplets due to Ostwald ripening and homogeneous and/or micellar nucleation, if micelles existed, triggered by radicals in the aqueous phase. For high hexadecane concentrations, Ostwald ripening was effectively retarded, and the miniemulsions were sufficiently stabilized against the degradation of molecular diffusion. The size distributions of the droplets and latex particles were almost identical. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4603–4610, 2006
Novel organosoluble polynorbornene bearing a polar, pendant, ester‐bridged epoxy group via living ring‐opening metathesis polymerization
Authors: Liaw Der‐Jang , Huang Ching‐Cheng , Fu Chun‐Wei
Published: June 2006

A novel organosoluble polynorbornene bearing a polar, pendant, ester‐bridged epoxy group [poly(oxiran‐2‐ylmethyl 2‐methylbicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate) (polyOMMC)] was prepared via the living ring‐opening metathesis polymerization (ROMP) of active norbornenes with a Ru catalyst. PolyOMMC exhibited excellent solubility in a variety of solvents. The number‐average molecular weight of polyOMMC linearly increased with the [M]/[I] ratio (where [M] is the monomer concentration and [I] is the initiator concentration), and a narrow polydispersity of 1.09–1.19 was observed; this was considered a living polymerization. When ROMP of oxiran‐2‐ylmethyl 2‐methylbicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate with [M]/[I] = 350 was carried out at 30 °C in CH2Cl2, the number‐average molecular weight (7.01 × 104; polydispersity index = 1.07) was close to the calculated molecular weight (7.28 × 104), and a diblock copolymer was observed after the addition of another monomer ([M]/[I] = 350) with an increase in the number‐average molecular weight (1.60 × 105; polydispersity index = 1.11), which was close to the calculated molecular weight (1.61 × 105). The modified polynorbornenes retained good solubility in methylene chloride, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, N,N‐dimethylacetamide, and N‐methyl‐2‐pyrrdione. High‐performance polynorbornenes with active epoxy groups could be designed with great potential for applications in photoresists, UV curing, and elastomers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4428–4434, 2006
Poly(p‐phenylene vinylene) derivatives containing triazole or oxadiazole segments: Connector effect in optical, electrochemical, and electroluminescent properties
Authors: Chen Shinn‐Horng , Chen Yun
Published: June 2006

To study the effect of connector structure between hole‐ and electron‐transporting segments, we synthesized and characterized new electroluminescent polymers P1–P7 consisting of hole‐transporting 1,4‐bis(hexyloxy)‐2,5‐distyrylbenzene (DSB: P1 and P2) and electron‐transporting 4‐(4‐(hexyloxy)phenyl)‐3,5‐diphenyl‐4H‐1,2,4‐triazole (TAZ: P3 and P4) or 2‐(2,5‐bis(hexyloxy)‐4‐(5‐phenyl‐1,3,4‐oxadiazol)phenyl)‐5‐phenyl‐1,3,4‐oxadiazole (DIOXD: P5–P7) segments linked by different connectors. The connectors between hole‐ and electron‐transporting segments are (1) 1,4‐phenylene in P3 and P5, (2) 1,4‐divinylbenzene in P4 and P6, and (3) 4,4′‐biphenyl in P7. Three corresponding end‐capped model polymers P1‐M, P2‐M, and P3‐M were also synthesized to evaluate the effect of end groups. From optimized semiempirical MNDO calculations, the adjacent benzene rings between DSB and TAZ or DIOXD chromophores in P3, P5, and P7 twist about 81°–89°. The effect of twisted architectures and connectors in optical and electrochemical properties for P1–P7 have been discussed by comparing with copolymers P1 and P2, which possess single bond or ether spacer as connectors. From cyclic voltammograms, the torsion in P3, P5, and P7 confines electron delocalization and leads to simultaneously enhanced hole and electron affinity as compared to those of P1 and P2. Furthermore, double‐layer light‐emitting diodes with a configuration of ITO/PEDOT:PSS/P1–P7/Al all reveal green–yellow electroluminescence with maximum luminance at 8–320 cd/m2 and their performances are greatly influenced by the connector's structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4514–4531, 2006
Poly(fluorenevinylene) derivatives by Heck coupling: Synthesis, photophysics, and electroluminescence
Authors: Mikroyannidis John A. , Yu Young‐jun , Lee Seung‐hun , Jin Jung‐il
Published: June 2006

Three new poly(fluorenevinylene) derivatives were synthesized, characterized, and used as emissive materials in light‐emitting diodes (LEDs). They were synthesized by Heck coupling of 9,9‐dihexyl‐2,7‐divinylfluorene with 2,7‐dibromo‐9,9‐dihexylfluorene, 2,3‐bis(4‐bromophenyl)quinoxaline, or 2,5‐bis(4‐bromophenyl)‐3,4‐diphenylthiophene to afford the polymers F, Q, and T, respectively. Polymers F and Q had medium number–average molecular weights (Mn ˜ 14,000) with relatively narrow polydispersity (1.3–1.6), while T was obtained as an oligomer (Mn ˜ 4000). All polymers were soluble in common organic solvents, such as tetrahydrofuran (THF), chloroform, dichloromethane, and toluene. They emitted blue‐greenish fluorescence light in dilute THF solution (444–491 nm), with photoluminescence (PL) quantum yields of 0.32–0.54, and in thin film (453–488 nm). LEDs with the configuration of ITO/PEDOT‐PSS/Polymer/Li:Al were fabricated and evaluated. The electroluminescence (EL) spectra of the Q and F polymers were very broad covering the blue–green–red region, whereas the spectrum of the polymer T was almost purely blue. The threshold electrical field for light emission of the devices was almost the same (˜1.75 MV/cm). The external quantum efficiency of the devices of polymers Q and F was about 1.0 × 10−3%, whereas that of polymer T was ˜3.0 × 10−5%. The fluorescence lifetime of polymers F and Q was significantly longer than that of the polymer T. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4494–4507, 2006
Polyampholyte terpolymers of amphoteric, amino acid‐based monomers with acrylamide and (3‐acrylamidopropyl)trimethyl ammonium chloride
Authors: Ezell Ryan G. , Gorman Irene , Lokitz Brad , Treat Neil , Mcconaughy Shawn D. , Mccormick Charles L.
Published: June 2006

Low‐charge‐density amphoteric copolymers and terpolymers composed of acrylamide, (3‐acrylamidopropyl)trimethyl ammonium chloride, and the amino acid derived monomers (e.g., N‐acryloyl valine, N‐acryloyl alanine, and N‐acryloyl aspartate) were prepared via free‐radical polymerization in aqueous media to yield terpolymers with random charge distributions and homogeneous compositions. Sodium formate (NaOOCH) was employed as a chain transfer agent during the polymerization to suppress gel effects and broadening of the molecular weight distribution. Terpolymer compositions were determined by 13C and 1H NMR spectroscopy. Terpolymer molecular weights and polydispersity indices were obtained via size exclusion chromatography/multi‐angle laser light scattering, and hydrodynamic diameter values were obtained via dynamic light scattering. The solution properties of low‐charge‐density amphoteric copolymers and terpolymers have been studied as a function of solution pH, ionic strength, and polymer concentration. The low‐charge‐density terpolymers display excellent solubility in deionized (DI) water with no phase separation. The charge‐balanced terpolymers exhibit antipolyelectrolyte behavior at pH values ≥(6.5 ± 0.2). As solution pH is decreased, these charge‐balanced terpolymers become increasingly cationic because of the protonation of the anionic repeat units. Charge‐imbalanced terpolymers generally demonstrate polyelectrolyte behavior, although the effects of intramolecular electrostatic interactions (e.g., polyampholyte effects) on the hydrodynamic volume are evident at certain values of solution pH and salt concentration. The aqueous solution behavior (i.e., globule‐to‐coil transition at the isoelectric point in the presence of salt and globule elongation with increasing charge asymmetry) of the terpolymers in the dilute regime correlates well with that predicted by the polyampholyte solution theories of Dobrynin and Rubinstein as well as Kantor and Kardar. Examination of comonomer charge density, hydrogen‐bonding ability, and spacer group (e.g., the moiety separating the ionic group from the polymer chain) indicates that conformational restrictions of the amino acid comonomers result in increased chain stiffness and higher solution viscosities in DI water and brine solutions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4479–4493, 2006
Homopolymerization of cyclic esters initiated by lanthanide isopropoxides supported by 2,2′‐ethylene‐bis(4,6‐di‐tert‐butylphenolate) ligands
Authors: Xu Xiaoping , Yao Yingming , Hu Mingyu , Zhang Yong , Shen Qi
Published: June 2006

Lanthanide isopropoxides supported by carbon‐bridged bisphenolate ligands of 2,2′‐ethylene‐bis(4,6‐di‐tert‐butylphenoxo) {[(EDBP)Ln(μ‐OPri)(THF)2]2, where Ln is Nd (1), Sm (2), or Yb (3) and THF is tetrahydrofuran} were synthesized by protic exchange reactions in high yields with Cp3Ln compounds as raw materials, and complex 1 was structurally characterized. Complexes 1–3 were shown to be efficient initiators for the ring‐opening polymerization of ε‐caprolactone (ε‐CL) and 2,2‐dimethyltrimethylene carbonate (DTC). Complexes 1–3 could initiate the controlled polymerization of ε‐CL, and the polymerization rate was first‐order with respect to the monomer. The influence of the reaction conditions on the monomer conversion, molecular weight, and molecular weight distribution of the resultant polymers was investigated. End‐group analyses of the oligomers of ε‐CL and DTC showed that the polymerization underwent a coordination–insertion mechanism. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4409–4419, 2006
Synthesis and properties of a new fluorine‐containing polybenzimidazole for high‐temperature fuel‐cell applications
Authors: Chuang Shih‐Wei , Hsu Steve Lien‐Chung
Published: June 2006

An amorphous, organosoluble, fluorine‐containing polybenzimidazole (PBI) was synthesized from 3,3′‐diaminobenzidine and 2,2‐bis(4‐carboxyphenyl)hexafluoropropane. The polymer was soluble in N‐methylpyrrolidinone and dimethylacetamide and had an inherent viscosity of 2.5 dL/g measured in dimethylacetamide at a concentration of 0.5 g/dL. The 5% weight loss temperature of the polymer was 520 °C. Proton‐conducting PBI membranes were prepared via solution casting and doped with different amounts of phosphoric acid. In the methanol permeability measurement, the PBI membranes showed much better methanol barrier ability than a Nafion membrane. The proton conductivity of the acid‐doped PBI membranes increased with increasing temperatures and concentrations of phosphoric acid in the polymer. The PBI membranes showed higher proton conductivity than a Nafion 117 membrane at high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4508–4513, 2006
Synthesis and characterization of liquid‐crystalline block copolymers with cyanoterphenyl moieties by atom transfer radical polymerization
Authors: Lee Kuan‐Wei , Wei Kung‐Hwa , Lin Hong‐Cheu
Published: June 2006

A series of new mesomorphic block copolymers composedofdifferentmacroinitiators, including poly(ethylene oxide), polystyrene, and poly(ethylene oxide)‐b‐polystyrene,and polymethacrylate with a pendent cyanoterphenyl group were synthesized through atom transfer radical polymerization. The number‐average molecular weights of the three diblock copolymers, determined by gel permeation chromatography, were 10,254, 9,772, and 15,632 g mol−1, and their polydispersity indices were 1.17, 1.28, and 1.34. The mesomorphic and optical properties of all the block copolymers were investigated, and they possessed a smectic A phase with mesophasic ranges wider than 100 °C. Moreover, X‐ray diffraction patterns provided evidence of the smectic A phase and the corresponding interdigitated packing of all the polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4593–4602, 2006
Fluorene copolymers containing bithiophene/2,5‐ or 2,6‐pyridine units: A study of their optical, electrochemical, and electroluminescence properties
Authors: Jung Young Kwan , Lee Jaemin , Lee Sang Kyu , Cho Hoon‐Je , Shim Hong‐Ku
Published: June 2006

Two alternating copolymers, poly[(2,5‐di(2‐thienyl)‐pyridine‐5,5′‐diyl)‐alt‐(9,9‐dioctylfluorene‐2,7‐diyl)], PFO‐TPy25T, and poly[(2,6‐di(2‐thienyl)‐pyridine‐5,5′‐diyl)‐alt‐(9,9‐dioctylfluorene‐2,7‐diyl)], PFO‐TPy26T, were synthesized by the Pd‐catalyzed Suzuki polymerization method. The pyridine units are present as trimeric monomers in these copolymers and have different connectivities to their two neighboring thiophenes, para‐ and meta‐linkages. We investigated the variations in the optical and electrochemical properties of the copolymers that arise from these different connectivities. The two polymers exhibit 5% weight loss above 410 °C and high glass transition temperatures (Tg: 113 °C for PFO‐TPy25T, 142 °C for PFO‐TPy26T). The UV–vis absorption maximum peaks of PFO‐TPy25T and PFO‐TPy26T in the solid state were found to be 449 and 398 nm respectively, with photoluminescence maximum peaks in the solid state of 573 and 490 nm respectively. Using cyclic voltammetry, we determined their energy band gaps: 3.08 eV for PFO‐TPy25T and 3.49 eV for PFO‐TPy25T. The cyclic voltammetry study of these polymers revealed that there are some differences. The electroluminescence (EL) properties of the copolymers were measured for the device configuration of ITO/PEDOT/polymers/Ca/Al. The device fabricated with the polymer containing 2,5‐pyridine exhibits pale orange emission, whereas the device fabricated with the polymer containing 2,6‐pyridine exhibits pale blue emission. The EL device fabricated with PFO‐TPy25T has a higher brightness (2010 cd/m2) and external quantum efficiency (0.1%) than the PFO‐TPy26T device (260 cd/m2, 0.008%), because it has a smaller energy barrier to the injection of charges from PEDOT and Ca into the HOMO and LUMO levels. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4611–4620, 2006
Synthesis and Characterization of Energetic 1,2‐Bis(Oxyamino)Ethane Salts
Authors: Hawkins Tommy , Hall Leslie , Tollison Kerri , Brand Adam , McKay Milton , Drake Gregory W.
Published: June 2006

The synthesis, characterization, theoretical calculations, and safety studies of energetic salts based on 1,2‐bis(oxyamino)ethane, (H2NOCH2CH2ONH2), were carried out. The salts were characterized by vibrational (infrared, Raman), multinuclear NMR studies (1H, 13C), differential scanning calorimetry (DSC), elemental analysis, and initial safety testing (impact and friction sensitivity). Single crystal X‐ray diffraction studies were carried out on the mono‐perchlorate and the double nitrate salts, revealing the expected structures.
Scaling of the Shaped Charge Jet Break‐Up Time
Authors: Hirsch Eitan
Published: June 2006

Since the formula for the shaped charge jet break‐up time was published on 1979 many attempts were made to interpret it and to make its use more efficient. It is shown herein that the Vpl parameter depends on the ratio of the liner thickness to the charge explosive diameter by the formula: 1/Vpl=13.9−101⋅(TL/CD), where TL is the liner thickness, CD is the explosive charge diameter and the numbers are for a published set of measurements with an OFE copper liner driven by COMP‐B explosive. To find how the numbers used in this formula change with the liner material and its metallurgical state and with the type of explosive, measurements should be made as prescribed herein. An attempt to begin explaining this formula is made in the discussion.
Modification/oxidation of GaAs surface in electrolytes for cell‐culture bio‐sensing devices
Authors: Ozasa Kazunari , Nemoto Shigeyuki , Hara Masahiko , Maeda Mizuo
Published: June 2006

The surface modification/oxidation of GaAs substrates in electrolytes has been investigated from the viewpoint of bio‐sensing devices using AlGaAs/GaAs high‐electron‐mobility‐transistor (HEMT) structures, where the cell culture directly on a bare gate‐surface is intended for a high sensitivity to cell‐viabilities such as adhesion or cell‐cell interaction, through nitric‐oxide concentration or charged‐peptide chemisorption. Although GaAs surface (gate surface of HEMT) was oxidized even in pure water under room light, we found that the oxide layer is not formed in the dark or removed with the existence of small amounts of NaH2PO4 (0.8 mM) in the solution. The photo‐excited oxidation and its etching by NaH2PO4 are discussed as well as the temporal change of the HEMT performance in solution. Cell adhesion on a bare GaAs surface was poor, but a surface modification by fibrionectin improved the cell adhesion, comparable to that on the conventional cell‐culture dishes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic conductivity and structural distortion at the interface between insulators SrTiO3 and LaAlO3
Authors: Maurice J.‐L. , Carrétéro C. , Casanove M.‐J. , Bouzehouane K. , Guyard S. , Larquet É. , Contour J.‐P.
Published: June 2006

When insulator LaAlO3 is grown by epitaxy onto a TiO2‐terminated {100} surface of insulator SrTiO3, the system obtained has a metallic character. This phenomenon has been associated with an electrostatic frustration at the interface, as {100} surfaces of SrTiO3 are neutral while those of LaAlO3 are polar, but its microscopic mechanism is not quite understood. Here, we present a structural characterisation of this interface by aberration‐corrected transmission electron microscopy. The unit cells at the interface appear elongated: we discuss this distortion in terms of electrostatic charge and extra carriers at the interface. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parallel Manipulation of Bifunctional DNA Molecules on Structured Surfaces Using Kinesin‐Driven Microtubules
Authors: Dinu Cerasela Zoica , Opitz Jörg , Pompe Wolfgang , Howard Jonathon , Mertig Michael , Diez Stefan
Published: June 2006

We have developed a technique to manipulate bifunctional DNA molecules: One end is thiolated to bind to a patterned gold surface and the other end is biotinylated to bind to a microtubule gliding over a kinesin‐coated surface. We found that DNA molecules can be stretched and overstretched between the gold pads and the motile microtubules, and that they can form dynamic networks. This serves as a proof‐of‐principle that biological machineries can be used in vitro to accomplish the parallel formation of structured DNA templates that will have applications in biophysics and nanoelectronics.
Succinic semialdehyde dehydrogenase (SSADH) deficiency: Molecular analysis in a South American family
Authors: Lemes Aida , Blasi Paola , Gonzales Gabriel , Russi Maria E. , Quadrelli Roberto , Novelletto Andrea , Malaspina Patrizia
Published: June 2006

We report the clinical, biochemical and molecular findings on the first documented patient with 4‐hydroxybutyric aciduria (4‐HBA, McKusick 271980) from Uruguay. The patient displayed a severe picture and turned out to be homozygous for a mutation (c.1226G < A) previously shown to be associated with null enzyme activity.
On the Provenance of the Holy Shroud of Lirey/Turin: A Minor Suggestion
Authors: FRIEDLANDER ALAN
Published: June 2006

This paper does not discuss the authenticity or antiquity of the Holy Shroud. It addresses the problem of its historical appearance in the 1350s and its antecedents, if any, before that date. It is suggested that the object owed its creation (if a replica) or its transmission into Europe (if genuinely a relic) to the efforts of members of the Franciscan order. It speculates particularly on the role of Spirituals of that order aligned with Fra Angelo Clareno and his associates. The conclusions do not assert but suggest the thesis, and advance it as a line of inquiry meriting further pursuit.
The Development of the Lord Bishop's Role in the Manx Tynwald
Authors: EDGE PETER W. , PEARCE C. C. AUGUR
Published: June 2006

The Isle of Man was a distinct diocese before it became a possession of the English crown in 1399. In the following centuries it retained not only a national legislature, the Tynwald, but the lord bishop of Sodor and Man. Ecclesiastical officers were to be found in Tynwald as early as 1614, and throughout the nineteenth century it included the lord bishop, the vicars-general and the archdeacon of the diocese. During the twentieth century the number of ecclesiastical officers in the legislature dwindled, until today only the lord bishop survives, and his position remains controversial.
An English Friendship and Italian Reform: Richard Morison and Michael Throckmorton, 1532–1538
Authors: OVERELL M. A.
Published: June 2006

This study sets the history of a friendship in the context of religious reform in Italy in the 1530s. Richard Morison and Michael Throckmorton were friends at the University of Padua but gradually became foes. In 1536 Morison returned to England to become Cromwell's propagandist and later Throckmorton began his dramatic career as Pole's agent. In Italy, however, both these young humanists had links with a group of reformers later called ‘spirituali’. Morison met them through contacts with Edmund Harvel and Bishop Cosimo Gheri. The discovery of Throckmorton's inventory shows that he owned books associated with Italian reform, including banned publications containing writings of the Northern Reformers. The rift between them was caused by political reformation in England, not religion in Italy.
Epistemic foundation of stable model semantics
Authors: LOYER YANN , STRACCIA UMBERTO
Published: June 2006

Stable model semantics has become a very popular approach for the management of negation in logic programming. This approach relies mainly on the closed world assumption to complete the available knowledge and its formulation has its basis in the so-called Gelfond–Lifschitz transformation. The primary goal of this work is to present an alternative and epistemic-based characterization of stable model semantics, to the Gelfond-Lifschitz transformation. In particular, we show that stable model semantics can be defined entirely as an extension of the Kripke-Kleene semantics. Indeed, we show that the closed world assumption can be seen as an additional source of ‘falsehood’ to be added cumulatively to the Kripke-Kleene semantics. Our approach is purely algebraic and can abstract from the particular formalism of choice as it is based on monotone operators (under the knowledge order) over bilattices only.
An entropy regularization method applied to the identification of wave distribution function for an ELF hiss event
Authors: Prot Olivier , Santolík Ondřej , Trotignon Jean‐Gabriel , Deferaudy Hervé
Published: June 2006

An entropy regularization algorithm (ERA) has been developed to compute the wave‐energy density from electromagnetic field measurements. It is based on the wave distribution function (WDF) concept. To assess its suitability and efficiency, the algorithm is applied to experimental data that has already been analyzed using other inversion techniques. The FREJA satellite data that is used consists of six spectral matrices corresponding to six time‐frequency points of an ELF hiss‐event spectrogram. The WDF analysis is performed on these six points and the results are compared with those obtained previously. A statistical stability analysis confirms the stability of the solutions. The WDF computation is fast and without any prespecified parameters. The regularization parameter has been chosen in accordance with the Morozov's discrepancy principle. The Generalized Cross Validation and L‐curve criterions are then tentatively used to provide a fully data‐driven method. However, these criterions fail to determine a suitable value of the regularization parameter. Although the entropy regularization leads to solutions that agree fairly well with those already published, some differences are observed, and these are discussed in detail. The main advantage of the ERA is to return the WDF that exhibits the largest entropy and to avoid the use of a priori models, which sometimes seem to be more accurate but without any justification.
Elastic scattering of hydrogen and deuterium atoms by oxygen atoms
Authors: Jamieson M. J. , Dalgarno A. , Wei L.
Published: June 2006

Interaction potentials of Yarkony (1992), matched to new dispersion potentials, are used in calculations by quantal and semiclassical methods of scattering and diffusion cross sections for elastic collisions between hydrogen and deuterium atoms and oxygen atoms, at energies up to 5 eV. Discrepancies among the published values and with the new results are resolved. The coefficients that describe mutual diffusion between hydrogen and oxygen and between deuterium and oxygen at temperatures up to 5000 K are calculated.
Day‐to‐day variability of the E layer
Authors: Moore Luke , Mendillo Michael , Martinis Carlos , Bailey Scott
Published: June 2006

Noontime day‐to‐day variability of ionosonde and incoherent scatter radar (ISR) measurements of the E layer are analyzed for two time periods: 9–27 March 1999 and 4 October–4 November 2002. E layer variability is found to be between 5 and 7% at midlatitudes for these periods. Polar latitudes demonstrate variability ranging from ∼7 to 50%, resulting primarily from a combination of photochemical and auroral processes. In order to understand the relative importance of the various sources that drive the variability in the E layer, a one‐dimensional time‐dependent photochemical model of the Earth's upper atmosphere is developed. The model is able to reproduce E layer electron density and variability for both time periods at a number of mid‐ and low‐latitude stations. It is shown that E layer variability is dominated by variations in the incident solar flux for mid‐ and low‐latitude stations, while auroral ionization processes are estimated to contribute roughly 30% of the total variability observed at polar stations. Changes in the solar declination over the time periods studied are responsible for a secondary source of E layer variability at midlatitudes and for a primary source at high latitudes. Day‐to‐day changes in neutral atmosphere species (including observed NO densities) contribute the least to overall E layer variations, except at low latitudes, where their contribution to variability is comparable to variability induced by changes in solar declination.
Alfvén‐cyclotron scattering of solar wind ions: Hybrid simulations
Authors: Gary S. Peter , Yin Lin , Winske Dan
Published: June 2006

This paper describes results from ensembles of hybrid simulations of steady, homogeneous, collisionless plasmas characterized by average solar wind parameters near 1 AU upon which damped, resonant Alfvén‐cyclotron fluctuations are imposed. The applied fluctuations propagate parallel to the background magnetic field Bo. The ensembles yield late‐time proton and alpha particle responses to such fluctuations as functions of the initial magnitude of the applied fluctuating magnetic field energy and the initial vαp/vA (where vαp is the alpha/proton relative speed and vA is the Alfvén speed). The simulations show a strong, consistent negative correlation between the alpha temperature anisotropy T⊥α/T∥α (where the directional subscripts refer to directions perpendicular and parallel to Bo) and vαp/vA. On average the simulations also show a weaker, positive correlation between the proton temperature anisotropy and vαp/vA. Both correlations are in agreement with statistical observations from the solar wind near 1 AU, thereby confirming earlier conclusions that such observations are signatures of Alfvén‐cyclotron scattering of ions in the solar wind.
The sedimentary and tectonic evolution of the Yinggehai–Song Hong basin and the southern Hainan margin, South China Sea: Implications for Tibetan uplift and monsoon intensification
Authors: Clift Peter D. , Sun Zhen
Published: June 2006

The Yinggehai–Song Hong basin is one of the world's largest pull‐apart basins, lying along the trace of the Red River fault zone in the South China Sea. South of Hainan Island this basin crosscuts the rifted margin of the northern South China Sea. In this paper we present for the first time a regional compilation of multichannel seismic reflection data from both the strike slip and rifted margins. The basins started to open after ∼45 Ma, especially after ∼34 Ma. The Yinggehai basin was folded and inverted in the middle Miocene, after 21 Ma in the north and 14 Ma in the south, before rapidly subsiding again after ∼5 Ma because of continued tectonism. This subsidence has caused shale diapirism, especially driven by associated sedimentation in the late Pliocene (2.6–2.0 Ma). Extension along the adjacent south Hainan margin shows preferential lower crustal extension, suggestive of lower crustal flow increasing toward the continent‐ocean transition during breakup. Sediment supply is reconstructed to peak in the middle Miocene, then falls between 14 and 10.3 Ma to reach a low in the late Miocene. However, rates rose again in the Pliocene‐Pleistocene. The Red River sediment budget is incompatible with climate models that propose stronger monsoon rains starting at 8 Ma or with large‐scale river capture away from the Red River after ∼10 Ma. Both lines of evidence point to major uplift in the Red River drainage being middle Miocene or older. The recent, preindustrial Red River carried much more sediment than the average Pleistocene accumulation rate, indicating modest sediment buffering onshore, at least in recent geologic time.
Magnetic domain observations on magnetite crystals in biotite and hornblende grains
Authors: Özdemir Özden , Dunlop David J.
Published: June 2006

Magnetic domain structures have been observed on magnetite crystals in 300 μm to 1 mm size biotite and hornblende grains separated from drill core samples of Precambrian granodiorite basement in southern Alberta, Canada. The crystals were mounted in epoxy, and the surface was polished, first mechanically and then with a suspension of amorphous SiO2. Domain structures were observed on 6–60 μm magnetite crystals using the Bitter colloid technique. Observed features include lamellar domains bounded by straight 180° walls, closure domains, bent walls, wavy structures, and areas without visible domains. Crystals ≤50 μm in size generally have simple domain patterns with domain walls parallel to the long axis of the crystal. We studied domain wall displacements in small isolated magnetites as a function of applied magnetic field up to 24 mT. The number of domains decreases with increasing external field. Some walls are relatively mobile and disappear by 20 mT. Other walls remain immobile; in some cases, crystal defects or inclusions are seen to pin these walls, or segments of walls. An interesting observation was made on a 5 × 25 μm elongated magnetite crystal formed in a crack in hornblende. Large quantities of magnetic colloid gathered at either end of the crystal because of the strong flux leakage and pole fields at these locations. Colloid was also concentrated where domain boundaries intersect the sides of the crystal. With increasing applied field the colloid spread out to form patterns tracing complete external flux closure loops.
Response of normal faults to glacial‐interglacial fluctuations of ice and water masses on Earth's surface
Authors: Hampel Andrea , Hetzel Ralf
Published: June 2006

Changes in surface loads during glacial‐interglacial cycles and the associated flexure and rebound of the lithosphere alter the stress field in actively extending regions and may lead to slip rate variations on normal faults. In particular, loading may cause a period of seismic quiescence that is followed by temporal clustering of earthquakes during and after unloading. Here we present a suite of finite element experiments to evaluate how the magnitude, distribution, and temporal evolution of the load, as well as rheological parameters of the lithosphere and asthenosphere, influence the response of a normal fault. The results show that the duration of the seismically quiet period during loading and the intensity of the slip rate increase during unloading are primarily controlled by the magnitude of the load. The time lag between the changes in loading and the reaction of the fault is mainly determined by the viscosity of the asthenosphere. Parameters that play only a minor role for the fault's response include the rate of load removal, fault strength, and the thickness of the lithosphere. Our results imply that earthquake recurrence models derived from Holocene slip histories may not be representative for the long‐term evolution of seismogenic faults.
Measurements of historical total ozone from the Chalonge‐Divan stellar spectrum program: A reanalysis of the 1953–1972 data and a comparison with simultaneous Dobson Arosa measurements
Authors: Griffin R. E. M. , Fioletov V. , McConnell J. C.
Published: June 2006

We report new determinations of total ozone obtained by reanalyzing a unique set of astronomical observations that were made in the mid‐20th century at observatories in France (Haute‐Provence) and Switzerland (Jungfraujoch) for the purpose of calculating nightly atmospheric extinction coefficients in the UV (Rayleigh scattering and total ozone) as part of a program to measure absolute stellar fluxes. Only a small fraction of the original ozone results, corresponding to data obtained during 1958–1959, are in the public domain at the World Ozone and Ultraviolet Data Centre; the rest were on handwritten sheets and were stored at Haute‐Provence. Both astronomical sites are close enough geographically to Arosa (Switzerland) that the respective ozone values can be compared directly. The comparison reveals a generally very close resemblance, even down to the pattern of daily variations, with a correlation coefficient of 0.78, but an overall negative bias of 6–7% in the stellar results. The bias appears to be slightly larger prior to 1958.
Martian north polar layered deposits stratigraphy: Implications for accumulation rates and flow
Authors: Fishbaugh Kathryn E. , Hvidberg Christine S.
Published: June 2006

We have used Mars Orbiter Camera (MOC) images and Mars Observer Laser Altimeter (MOLA) data to correlate specific layers within the upper ∼500 m of the Martian north polar layered deposits in many troughs. Using these correlation results, we derive relative accumulation rates across the polar layered deposits and through time. We identify two major layer sequences, one lying stratigraphically above the other, each consistent with an overall curving downward layer structure with shallow slopes but with significant localized variations in layer height. Major disruptions of stratigraphy (such as angular unconformities) do not appear within the correlated layer sequences. On local and broad scales, each layer sequence exhibits a different relative accumulation rate pattern, indicating that this rate has not remained constant through time and has been affected by localized processes. The overall pattern of the lower layer sequence is similar to that of a classic terrestrial ice sheet, with a decreasing relative accumulation rate away from the center of the polar layered deposits southward. The upper layer sequence exhibits no obvious overall trends. We also compare our correlation results to predictions of the effects of simple ice flow on layer structure, finding that mass balance patterns have overprinted any effects of large‐scale ice flow. Flow has not been significant, compared to mass balance, in forming the overall structure of the correlated layers.
Initial observations of low‐frequency magnetic fluctuations in the Martian ionosphere
Authors: Espley J. R. , Delory G. T. , Cloutier P. A.
Published: June 2006

Using Mars Global Surveyor magnetometer/electron reflectometer measurements, we report initial observations of low‐frequency magnetic fluctuations in the Martian ionosphere. We find that the waves have dominant frequencies between 0.01 and 1 Hz and are observed both close to and far from crustal magnetic fields. These waves are possibly related to magnetosonic perturbations produced at higher altitudes in the Mars–solar wind interaction. These fluctuations have implications for understanding the physics of the ionosphere and potentially could also help characterize electromagnetically active atmospheric phenomena such as dust devils and dust storms. The presence of such fluctuations in the Martian ionosphere is also an indication of the plausibility of using low‐frequency electromagnetic methods, such as the magnetotelluric technique, to probe the deep subsurface. One potential result of such an investigation would be the identification of any subsurface liquid water that might be present within the first several hundred meters to the first few kilometers of the subsurface.
Characteristic Features of in vivo Skin Microvascular Reactivity in CADASIL
Authors: Gobron Claire , Vahedi Katayoun , Vicaut Eric , Stucker Olivier , Laemmel Elisabeth , Baudry Nathalie , Bousser Marie Germaine , Chabriat Hugues
Published: June 2006

CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) is caused by mutations in the Notch3 receptor expressed at the surface of vascular smooth muscle cells. The functional consequences of the disease at the peripheral microcirculation level are incompletely elucidated. In this study, we aimed to assess, in vivo, the endothelium-dependent and independent vasodilation of the skin microvasculature in CADASIL patients. Twenty-three affected subjects were compared with 23 gender and age-matched controls. The brachial artery endothelium-dependent and endothelium-independent vasodilation were assessed after forearm cuff occlusion and nitroglycerin administration. Skin vasoreactivity to transcutaneous administration of acetylcholine and sodium nitroprussiate, and after postocclusive hyperemia were measured by Laser Doppler flowmetry. The maximum changes in the diameter of the brachial artery after the cuff release or after nitroglycerin administration did not differ between patients and controls. With iontopheresis, only the peak value of the dose response was found decreased in normocholesterolemic patients after nitroprussiate administration. The postocclusive test revealed a large increase of the time to peak value and whole duration of the hyperemic response in CADASIL patients. The results of this study show that the skin vasoreactivity is altered in CADASIL. Particularly, the kinetics of reactive hyperemia after cuff occlusion is dramatically changed with a lengthened and delayed response. This characteristic pattern may be related to the specific ultrastructural modifications related to Notch3 gene mutations involving smooth muscle cells in the microvasculature.
Observation and manipulation of the as-grown maze domain structure in lead germanate by scanning force microscopy
Authors: Shishkin E. I. , Shur V. Ya. , Schlaphof F. , Eng L. M.
Published: June 2006

The ferroelectric domain structure of single crystalline Pb5Ge3O11 was inspected and manipulated using piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM). The irregularly shaped three-dimensional maze reflecting the as-grown domain structure on the micron and submicron scale was resolved with both PFM and KPFM. The temporal stability and recovery of that equilibrium structure was tested with macroscopic and local electric fields. Fractal analysis was applied for quantitative characterization of the complicated domain geometry. While spatially extended fields lead to a partial decay of the maze structure, local electric fields applied by the PFM tip result in addition in pronounced surface charging. The time constants of charge decay were extracted by KPFM and could be attributed to mobile charge redistribution and backswitching.
Optical properties of tetragonal photonic crystal synthesized via template-assisted self-assembly
Authors: Jin Chongjun , Li Zhi-Yuan , McLachlan Martyn A. , McComb David W. , De La Rue Richard M. , Johnson Nigel P.
Published: June 2006

A (001) oriented three-dimensionally periodic photonic crystal, free of cracks, has been fabricated via a modified template-assisted colloidal self-assembly method with polystyrene spheres. Analysis of the opal-type crystals has revealed the structure to be noncubic. This is a face-centered tetragonal (fct), (001) oriented photonic crystal. The optical properties of the crystals have been characterized at near-normal incidence by reflectance spectroscopy. It is found that the photonic stop band shifts to shorter wavelengths compared with an identical cubic structure oriented along the (001) direction. We have also simulated the stop band behavior of such fct crystals and their inverse silicon analogs, revealing that the polymer opal could provide an inverse template for the formation of photonic crystals with a complete band gap.
The role of charge trapping at grain boundaries on charge transport in polycrystalline chemical vapor deposited diamond based detectors
Authors: Hearne S. M. , Trajkov E. , Jamieson D. N. , Butler J. E. , Prawer S.
Published: June 2006

We report a detailed investigation of the trapping and release of charge carriers from grain boundaries in polycrystalline diamond grown by chemical vapor deposition (poly-CVD). A model for charge trapping and release is presented for samples which display very different bulk characteristics as determined by photoluminescence, dark conductivity, and thermally stimulated current measurements. Experimental studies were performed as a function of temperature and applied electric field using ion beam induced charge to map the charge collection efficiency of charge induced by a scanned, focused, 2MeV He+ microprobe. Even though the carrier velocity and charge collection efficiency should begin to saturate at electric fields above 1×104V∕cm, the efficiency was found to increase by a factor of 3 when the electric field is increased to greater than 1×105V∕cm. A model based on the localized enhancement of the electric field caused by trapped charge at grain boundaries is found to account for this unexpected result. Further, we find that this localized variation in electric field strongly affects charge transport in poly-CVD diamond and is therefore an important consideration for optimizing detector performance.
Spectral characteristics of computer screen photoassisted classification
Authors: Filippini D. , Lundström I.
Published: June 2006

The computer screen photoassisted technique (CSPT) is a practical method for the classification of colored or fluorescent substances such as those present in bioassays but using standard computer sets and regular web cameras as all instruments. It is empirically known that the performance of the CSPT classification depends on the composition of the illuminating sequences displayed by the computer screens during the measurements, and by the way that substance fingerprints from these measurements are composed. Here the illuminating conditions are examined with the help of a CSPT model that allows to examine the physical grounds of optimum illuminating sequences different from just three screen primaries and to assess the limitations and importance of longer illuminating sequences in practical determinations.
Passive optical diagnostic of Xe propelled Hall thrusters. II. Collisional-radiative model
Authors: Karabadzhak George F. , Chiu Yu-hui , Dressler Rainer A.
Published: June 2006

A collisional radiative model is presented for analyzing the xenon-propelled Hall thruster optical radiation based on apparent electron and ion-impact emission cross sections associated with lines in the visible and near-infrared region of the spectrum. The emission cross sections of selected near-infrared emission lines are incorporated in a collisional-radiative model. The effect of stepwise excitation via metastable states on the derived line intensities for emissions from XeI 5p56p(6p′) levels is evaluated. Meanwhile, visible XeII emissions are shown to provide plasma densities at high electron temperature conditions. The electron temperature and spatial ion number density distribution were determined from the luminescence spectra measured in the discharge and plume near-field plasma of the Hall thruster, the TSNIIMASH D-55 anode layer thruster. The results are in good agreement with the probe measurement data and simulations reported in the literature for the same thruster. The analysis of the Hall thruster XeI near-infrared spectra demonstrates that the neglect of ion-atom collisions results in an erroneous electron temperature determination at electron temperatures below 10eV.