bluuebunny/crossref_metadata_2025 huggingface dataset:
Exciton dissociation in conjugated polymers
Authors: Arkhipov Vladimir , Bässler Heinz , Emelyanova Evgenia , Hertel Dirk , Gulbinas Vidmantas , Rothberg Lewis
Published: May 2004

In conjugated polymers, a majority of photogenerated charges form metastable geminate pairs (GPs), of which only some fraction can dissociate completely. Both the yield of GP photogeneration and the probability of further dissociation of GPs into free charges depend upon an external electric field. In the present article we discuss several experimental methods to detect the existence of geminate pairs such as delayed field collection of charges, field quenching of fluorescence, and field‐assisted photoinduced optical absorption. It is shown that the field dependences of the exciton dissociation into GPs and of the free carrier photogeneration yield are rather similar. This is in contrast with the traditional Onsager theory, which assumes field‐independent yield of primary photoionization and disregards the field dependence of the initial separations between carriers in GPs.
Luminescence properties of PPV derivatives bearing substituted carbazole pendants
Authors: Park Jong Hyun , Kim Kyungkon , Hong Young‐Rae , Jin Jung‐Il , Sohn Byung‐Hee
Published: May 2004

A series of PPV derivatives bearing substituted and unsubstituted carbazole and 2‐ethylhexyloxy pendants were prepared and their photo‐ (PL) and electroluminescence (EL) properties were studied. Substituted carbazole structures were N‐phenylcarbazole and 3,6‐dimethoxycarbazole. The substituents on the carbazole pendants caused little change in UV‐vis absorption, PL, and EL when compared with the polymer bearing the unsubstituted carbazole pendants. The presence of the benzene ring between the main chain and the carbazole pendant increased the threshold electric field in EL. We could obtain maximum brightness of ca. 17,000 ‐ 30,000 cd/m2 for the polymers carrying the unsubstituted and dimethoxy substituted carbazole pendants.
Manifestation of electrode surface states in molecular conduction
Authors: Fagas Giorgos , Gutierrez Rafael , Richter Klaus , Grossmann Frank , Schmidt Rüdiger
Published: May 2004

We present a conduction mechanism across molecular junctions which derives from conductance resonances that are not associated with particular molecular orbitals. Instead, the resonances are induced by states localized at the surface of the electrodes. To this end, we studied the conductance of a C60 molecule bridging two carbon nanotubes. A simple tight‐binding model is employed to investigate analytically the basic features of the effect.
Novel tunable optical properties of liquid crystals, conjugated molecules and polymers in nanoscale periodic structures as photonic crystals
Authors: Yoshino Katsumi , Takeda Hiroyuki , Kasano Masahiro , Satoh Shigenori , Matsui Tatsunosuke , Ozaki Ryotaro , Fujii Akihiko , Ozaki Masanori , Kose Akira
Published: May 2004

Tunability of optical properties such as transmission and reflection by temperature and applied voltage has been demonstrated in synthetic opals and inverse opals like three‐dimensional photonic crystals infiltrated with liquid crystals, conjugated molecules and polymers, in accordance with theoretical calculation. A new type of tunability based on uncoupled mode in a two‐dimensional photonic band gap influenced by the field‐dependent anisotropy in liquid crystals has also been demonstrated theoretically. Spectral narrowing and lasing have been observed in these opals infiltrated with conducting polymers and fluorescent dyes like three‐dimensional photonic crystal and fluorescent dye‐doped cholesteric and ferroelectric liquid crystal as one‐dimensional photonic crystal. These lasing wavelength can be controlled by the applied voltage. Laser emission was also realized with conducting polymer on a surface relief grating formed on an azo‐polymer film by interference optical beam.
Rough electrode surface: effect on charge carrier injection and transport in organic devices
Authors: Novikov Sergey V.
Published: May 2004

The effect of electrode roughness on charge carrier injection and transport is considered. An explicit formula connecting the roughness profile of an electrode with the distribution of the electric field at its surface (and the electrostatic potential in the bulk of transport layer) is derived for the case of smooth roughness, when the typical height of roughness element is small in comparison with its size across the surface (this is a very typical situation). This formula gives us an opportunity to measure the electrode surface profile (e.g., by AFM) and then to calculate various injection properties of this particular electrode for any kind of injection. General properties of the electrode ‐ organic layer interface in the case of significant (not smooth) roughness are considered and a suitable numeric procedure for the calculation of the surface electric field distribution is proposed. It is also shown that rough surface of electrodes generates an additional energy disorder in the bulk of transport layer. This principal result indicates that the electrode roughness affects not only carrier injection but carrier transport as well. Roughness‐induced energetic disorder produces a channel‐like structure in the vicinity of the electrode, thus providing separation of electrons and holes. Such separation should decrease the charge recombination rate and, hence, the emitting efficiency of light emitting devices. At the same time, the separation is favorable to solar cells.
Degradation effects in polymer light emitting devices due to heat treatment
Authors: Janssen Frank , Sturm Marco , van Ijzendoorn Leo , van der Gon Arnoud Denier , Schoo Herman , de Voigt Martien , Brongersma Hidde
Published: May 2004

The characteristics of polymer light emitting diodes (PLEDs) (ITO/PPV/Ca) depend strongly on the conditions during preparation and operation. We studied the effects of heat treatment (during and after preparation) of PLEDs with OC1C10‐PPV as active layer. PLEDs showed a reduction of both the current and the light output to 40 % after annealing for only 30 min at 65 °C. Effects on I‐V characteristics were studied by measuring single carrier devices (hole‐ and electron‐dominated devices). The current reduction after heat treatment can be ascribed to degradation of the ITO/PPV and the Ca/PPV interfaces.
Space charge distribution in luminescent conjugated polymers
Authors: Geschke Dieter , Feller Frank , Monkman Andy P.
Published: May 2004

We have used for the first time the laser intensity modulation method (LIMM) to resolve the depth profile of space charges in films of poly[(2‐(2‐ethylhexyl)‐5‐methoxy‐1,4‐phenylene)vinylene] (MEH‐PPV), poly(pyridine‐2,5‐diyl) (PPY) and poly(fluorene) (PFO). The results demonstrate that in conjugated polymers space charges can not only be created but also stored permanently.
Luminescence properties of epoxy resins modified with a carbazole derivative
Authors: Mandowska Ewa , Mazela Wojciech , Czub Piotr , Mandowski Arkadiusz , Pielichowski Jan , Świątek Józef
Published: May 2004

Luminescence properties of a new material ‐ epoxy resin with added 9‐(2,3‐epoxypropyl)carbazole (REPK) were studied. Absorption and photoluminescence (PL) spectra of REPK are compared with those of poly(N‐vinylcarbazole) (PVK). PL in REPK is shifted to shorter wavelengths. Its intensity is higher than in PVK. REPK emits light in the range from 330 nm to 470 nm. PL spectrum of REPK could be well deconvoluted for four emission bands.
Electroluminescence and charge photogeneration in poly(9,9‐dihexadecylfluorene‐2,7‐diyl) and its blends
Authors: Cimrová Věra , Výprachtický Drahomír
Published: May 2004

Photoluminescence, electroluminescence (EL), charge photogeneration and transport were studied in poly(9,9‐dihexadecylfluorene‐2,7‐diyl) (PFC16), poly[(2,5‐dihexadecyl‐1,4‐phenylene)(1,4‐phenylene)] (PPPC16) and their blends. Blending of PFC16 with PPPC16 led to a significant improvement of the EL efficiency and stability compared with the devices fabricated from the neat polymers. Efficient blue and white light‐emitting devices (LEDs) were fabricated using the blends. The increase in the EL efficiency was attributed to modification of the charge injection, transport and recombination properties in the blend.
Effects of mechanical and thermal stresses on electric degradation of polyolefins and related materials
Authors: Mamedov Shaval , Alekperov Vilayet , Can Nursel , Aras Faruk , Yilmaz Gunes
Published: May 2004

Degradation under the simultaneous effects of mechanical stress and temperature in polyolefins (PE, PP), composites on their basis (PE+PP fibre, PP+PP fibre, PP+glass fibre) and radiation low‐density polyethylene (X‐LDPE) used in high‐voltage cables obeys the thermofluctuation theory of Zhourkov (in certain σ and τ0 intervals) based on the theory of Arrhenius is presented in the following form:

τσ = τ0 exp[(U0 − γσ)/ RT] (1)

where τ is durability. τ0 is a constant (10−12‐10−13s) equal to period of vibrations of atoms around equilibrium position, U0 is the activation energy of the mechanical destruction process (at σ = 0), γ is a structure‐sensitive parameter, T is absolute temperature and R is universal gas constant. Electric degradation under the effects of electric field and temperature in the materials mentioned above obeys the equation:

τE = τ0 exp[(W0 − χE)/ RT] (2)

Here, τE, W0 and χ are analogous to τσ, U0 and γ, respectively.

It is assumed that the following equation is valid under the simultaneous effects of E, σ and T:

τσ,E = τ0 exp[(U0 − (γσ + χE))/ RT]. (3)

electric degradation
Oxidation state and proton doping level in copolymers of 2‐aminobenzoic acid and 2‐methoxyaniline
Authors: Mav Ida , Žigon Majda , Vohlídal Jiří
Published: May 2004

UV‐vis spectra of homopolymers and copolymers of 2‐aminobenzoic acid (OAB) and 2‐methoxyaniline (OMA) were analyzed in order to obtain information about the oxidation state and proton doping level of these polymers. Dimethyl sulfoxide (DMSO) was used as a solvent in which protonated forms of polyanilines are preserved and a mixture of N‐methyl‐2‐pyrrolidone and triethylamine (0.5 %) as a solvent (NMP/TEA) in which polyanilines are assumed to be non‐protonated. Polymers were prepared in the emeraldine salt form, externally doped with HCl. It was found that only external doping is eliminated in NMP/TEA while internal doping by carboxylate groups bound in OAB units remains operative. Since doped quinoid units do not contribute to the quinoid band (Q‐band at 630 nm), the intensity ratio of the Q‐band and benzenoid band (B‐band at 320 nm) cannot be simply correlated with the oxidation state of poly(OMA‐co‐OAB) copolymers in contrast to poly(OMA) and polyaniline. Spectra of copolymers with less than 60 % of OMA units as well as those of poly(OAB) in DMSO and NMP/TEA are almost identical due to internal doping, which is proposed to lead to structures in which main‐chain protons are coulombically bound with immobile carboxylate anions. In the spectra of copolymers with less than 60 % of OMA units, a well‐resolved band occurs at 500 nm, which can be ascribed to alternating or close‐to‐alternating sequences of OMA and OAB units.
Photoelectric properties of tetracene‐pentacene heterojunction
Authors: Signerski Ryszard , Jarosz Grażyna , Godlewski Jan
Published: May 2004

We investigated vacuum‐evaporated sandwich systems formed by two organic layers of pentacene and tetracene. We measured spectral dependences of photovoltaic short‐circuit currents and photocurrents as well as current‐voltage dependences. In the case of systems equipped with Au and CuI electrodes the structure of spectral characteristics is determined by exciton release of trapped charge carriers either in the bulk of tetracene or near tetracene‐pentacene interface and by photogeneration in pentacene layer. For systems with two Au electrodes we can also observe an influence of exciton injection of holes into tetracene on spectral characteristics. The measurements of dark current‐voltage characteristics allow to observe the presence of a potential barrier between tetracene and pentacene.
Studies of host‐guest thin films of corona‐poled betaine‐type polar molecules by kelvin probe technique and atomic force microscopy
Authors: Dobulans Rorijs , Cepite Daiga , Fonavs Egils , Muzikante Inta , Tokmakov Andrey , Erts Donats , Polakov Boris
Published: May 2004

In this work betaine‐type molecules were investigated. As a result of the asymmetry of charge distribution, molecules possess in the ground state a considerable permanent dipole moment. The decay of surface potential of poled polymer films is dependent at least on two relaxation processes. The influence of glass transition of PMMA on thermal dependence of the surface potential is shown. The transition temperature, where no changes of the surface potential appeared, is related to glass transition temperature of the host‐guest system. The topography of the film surface was obtained by AFM.
Generation of charge carrier pairs in tetracene layers
Authors: Obarowska Malgorzata , Signerski Ryszard , Godlewski Jan
Published: May 2004

The mechanism of negative and positive charge carrier generation by light absorption in tetracene layers has been studied. We conclude that there are different processes determining electron and hole production. Positive charge carriers are produced without recombination while the negative charge carrier generation depends strongly on the recombination process. The experimental data for charge carrier generation in tetracene layers are treated theoretically taking into account photogeneration, recombination of charge carriers, trapping and transport processes inside the sample.
Properties of optically addressed liquid crystal spatial light modulators studied by mach‐zehnder interferometry
Authors: Komorowska Katarzyna , Miniewicz Andrzej , Parka Janusz
Published: May 2004

In this work optically addressed liquid crystal spatial light modulators are experimentally investigated. Local reorientation of molecules in the modulator and local changes of effective refractive index neff (x,y) are induced by modulated light intensity I (x,y). We present preliminary results of measurements of phase shifts in optically addressed liquid crystal panels using a Mach‐Zehnder interferometer. Experiments were performed for the panels filled with nematic and dye‐doped nematic liquid crystals. Optical addressing was realized by Ar+ laser beam (λ = 514.5 nm) while the reading beam was supplied by He‐Ne laser (632.8 nm). The operation voltage was in the range 4 ‐ 20 V. The total phase shift under the influence of addressing light for the studied systems was 2 ‐ 6 pagr;, sensitivity to the addressing light ∼ μW/cm2 per 2π phase change and speed of response to the light was 20 ms ‐ 30 s with total recovery time 0.5 ‐ 120 s.
Optical spectroscopy of polysilylene films
Authors: Demchenko Yevhen V. , Klimovič Josef , Nešpůrek Stanislav
Published: May 2004

Luminescence of poly[cyclohexyl(methyl)silylene] films was studied by time‐resolved emission spectroscopy at temperatures from 15 K to 300 K. The main short‐wavelength peak, shifted with rising temperature to lower energies, showed time features typical of an energy donor. Three weak emission centres were found in the visible spectral region. They decayed more slowly having the time features of an energy acceptor. The rise in temperature made both the energy transfer and extension of the effective ‐conjugation length more efficient. Model calculations of the chain conformation energy showed the close‐to‐all‐trans and gauche helix minima for iso‐ and syndiotactic sequences and barriers between them.
The role of micelles of multiblock copolymers of ethylene oxide and propylene oxide in ion transport during acid bright copper electrodeposition
Authors: Tabakova Nadya , Pojarlieff Ivan , Mircheva Vera , Stejskal Jaroslav
Published: May 2004

The role of micelle formation in the levelling activity of electrolytes for copper electrodeposition was investigated. It was established that micelle formation in the electrolytes caused a dramatic increase in the degree of levelling. The effect takes places via the solubilization of the disodium bis(sulfopropyl) disulfide brightener in copolymer micelles and changes in the distribution of the brightener on cathode surface. The positive effect of a conducting‐polymer additive, a colloidal polyaniline dispersion, on the brightness of electrodeposited copper coatings is discussed.
Pyrazoloquinolines – alternative chromophores for organic LED fabrication
Authors: Niziol Jacek , Danel Andrzej , Gondek Ewa , Armatys Pawel , Sanetra Jerzy , Boiteux Gisele
Published: May 2004

In this paper the synthesis of some new chromophores which could be used in polymer/organic LED fabrication are presented. All of them are pyrazoloquinoline (PAQ) derivatives. Their emission properties were tuned by side group substitution. They were characterized by absorption and photoemission spectroscopy. Some were used, dispersed in poly(N‐vinylcarbazole) (PVK) matrix, as the emissive layer in LED structures.
Influence of morphology on electric conductance in poly(ethylene naphthalene‐2,6‐dicarboxylate)
Authors: Chavez Jose Fidel , Martinez‐Vega Juan Jorge , Zouzou Noureddine , Guastavino Jean
Published: May 2004

Polymers find an important field of application in the electrical industry because of their utilization as insulators and dielectrics. The challenge over the last several years has been to make electrical compounds smaller in size. In that way the material morphology is of strategic importance in the performance of new components in relation to their geometry. Therefore, it is important to know the influence of different types of stress on electric properties of the materials.

We have studied the influence of the crystallinity on electric conductance of poly(ethylenenaphthalene‐2,6‐dicarboxylate) (PEN), which is increasingly replacing some dielectrics (polypropylene and PET) in certain electric applications.

Starting from an amorphous PEN, samples with various crystallinities were obtained and analyzed using DSC in order to determine their thermal characteristics.

Moreover, measurements of charge and discharge currents were carried out on PEN samples to characterize their electric properties. The steady state current observed after 120 min, in response to the electric field, shows an increase in the insulator resistivity with the crystallinity. The increase in the crystallinity favors a decrease in the free volume, so the movement of charges is restricted especially by the species of large sizes.
Vibration‐induced energy relaxation in two‐level system
Authors: Menšík Miroslav , Nešpůrek Stanislav
Published: May 2004

Energy decay in a general two‐level electronic system coupled to a vibrational harmonic mode interacting with a thermal bath is studied theoretically. The model assumes a general form of the off‐diagonal elements (in the electronic basis) of the vibrational‐electronic interaction. The cases for constant, linear, and quadratic dependence with respect to the vibrational displacement are investigated. For short‐time regime, fast oscillations corresponding to a coherent energy exchange between electrons and vibrations appear. Their frequency Ω corresponds to the energy difference (ħΩ) between electronic levels. Additionally, for the case of linear or quadratic coupling, the amplitude modulation of the oscillations with the frequency ω equal to that of vibrational motion is found.
Smoking and Parkinson's disease: Systematic review of prospective studies
Authors: Allam Mohamed Farouk , Campbell Michael J. , Hofman Albert , Del Castillo Amparo Serrano , Fernández‐Crehuet Navajas Rafael
Published: May 2004

We estimated the pooled risk of tobacco smoking for Parkinson's disease (PD). Inclusion criteria included systematic searches of MedLine, PsycLIT, Embase, Current Contents, previously published reviews, examination of cited reference sources, and personal contact and discussion with several investigators expert in the field. Published prospective studies on PD and cigarette smoking. When two or more studies were based on an identical study, the study that principally investigated the relationship or the study that was published last was used. Seven prospective studies were carried out between 1959 and 1997, of which six reported risk estimates. Four cohorts were based on standardised mortality rates, which were exclusively of male. Only one study included risk estimates for both males and females separately. The risk of ever smoker was 0.51 (95% confidence interval, 0.43 to 0.61). There was an obvious protective effect of current smoking in the pooled estimate (relative risk, 0.35; 95% CI, 0.26–0.47). Former smokers had lower risk compared with never smokers (relative risk, 0.66; 95% CI, 0.49–0.88). Although our pooled estimates show that smoking is inversely associated with the risk of PD, the four prospective studies that were based on follow‐up of mortality of smokers had many limitations. Further studies evaluating the association between smoking and PD in women are strongly needed. © 2004 Movement Disorder Society
Asymmetric hydration of alkenes catalyzed by wool‐palladium complex
Authors: Xue Lei , Jia Bin , Tang Li , Ji Xiao Feng , Huang Mei Yu , Jiang Ying Yan
Published: May 2004

A wool‐palladium complex has been found to be able to catalyze the asymmetric hydration of 1‐octene to (S)‐(+)‐2‐octanol and 1‐decene to (R)‐(+)‐2‐decanol under 1 atm N2 and at 70°C. The optical yields were greatly affected by Pd content in wool‐palladium complex, reaction time and so on, when the proper conditions were selected, (S)‐(+)‐2‐octanol and (R)‐(+)‐2‐decanol could be obtained in 83.2 and 75.6%e.e. optical yield respectively. This chiral natural biopolymer‐palladium complex catalyst was very easy to prepare and could be reused several times without appreciable change in catalytic activity. Copyright © 2004 John Wiley & Sons, Ltd.
Ion conductive characteristics of DNA containing PEO chains covalently bound on nucleic acid bases
Authors: Nishimura Naomi , Kokubo Satoko , Ohno Hiroyuki
Published: May 2004

In order to prepare flexible and ion conductive deoxyribonucleic acid (DNA) films without phase separation, DNA was modified with poly(ethylene oxide) (PEO). PEOs with molecular weight of 150 to 2000 were fixed to the amino groups of nucleic acid bases in DNA (PEO‐DNA). Brittle DNA films turned flexible after PEO modification, and the highest ionic conductivity was obtained when PEO with molecular weight of 1000 was modified. Though Na+, counter cation of phosphate group, was expected to migrate in these PEOx‐DNA hybrids as a carrier ion, ionic conductivity was only 1.3 × 10−6 S cm−1. Addition of salts to PEO1000‐DNA considerably improved the ionic conductivity, and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) was the best salt for this purpose. When NaTFSI, 5 mol% to the oxyethylene (OE) unit, was mixed with PEO1000‐DNA, the highest ionic conductivity of 1.77 × 10−5 S cm−1 was observed at 30°C. Copyright © 2004 John Wiley & Sons, Ltd.
A comparative study of thermal ageing characteristics of poly(ethylene‐co‐vinyl acetate) and poly(ethylene‐co‐vinyl acetate)/carbon black mixture
Authors: Çopuroğlu Mehmet , Şen Murat
Published: May 2004

In this comparative study, the effect of carbon black (CB) on the thermal ageing characteristics of poly(ethylene‐co‐vinyl acetate) (EVA) was investigated. EVA, containing 13% vinyl acetate (VA), and poly(ethylene‐co‐vinyl acetate)/carbon black mixture (EVA/CB) containing 13% VA and 1% CB were aged at 85°C in air up to 30 weeks. Sol‐gel analysis experiments were made to determine the percentage gelation of both virgin and aged samples. FT‐IR measurements were performed to follow the chemical changes which took place in the samples during ageing. Dynamic and isothermal thermogravimetric studies were performed for determination of the thermal stabilities of virgin and aged samples.

Sol‐gel analysis results showed that EVA itself has a tendency to form a gel under thermal treatment, whereas EVA/CB never becomes a gel when being thermally aged under the same conditions. As a result of FT‐IR measurements, some oxidation products such as ketone, lactone and vinyl species were observed through thermal ageing of EVA. It is also clear that these kind of oxidation products did not appear to a considerable extent in EVA/CB. Thermal analysis experiments exhibit that thermal stability of EVA decreased through thermal ageing; whereas that of EVA/CB remained almost unchanged. Copyright © 2004 John Wiley & Sons, Ltd.
Fluorinated polyamides and poly(amide imide)s based on 1,4‐bis(4‐amino‐2‐trifluromethylphenoxy)benzene, aromatic dicarboxylic acids, and various monotrimellitimides and bistrimellitimides: Syntheses and properties
Authors: Yang Chin‐Ping , Chen Ya‐Ping , Woo E. M.
Published: May 2004

A CF3‐containing diamine, 1,4‐bis(4‐amino‐2‐trifluromethylphenoxy) benzene (I), was prepared from hydroquinone and 2‐chloro‐5‐nitrobenzotrifluoride. Imide‐containing diacids (Va–h and VIa,b) were prepared through the condensation reaction of amino acids, aromatic diamines, and trimellitic anhydride. Then, a series of soluble fluorinated polyamides (VIIa–h) and poly(amide imide)s (VIIIa–h and Xa,b) were synthesized from I with various aromatic diacids (IIa–h) and imide‐containing diacids (Va–h and VIa,b) via direct polycondensation with triphenyl phosphate and pyridine. The polyamides and poly(amide imide)s had inherent viscosities of 1.00–1.70 and 0.79–1.34 dL/g, respectively. All the synthesized polymers showed excellent solubility in amide‐type solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, and N‐dimethylformamide and afforded transparent and tough films via solvent casting. Polymer films of VIIa–h, VIIIa–h, and Xa,b had tensile strengths of 91–113 MPa, elongations to break of 8–40%, and initial moduli of 2.1–2.8 GPa. The glass‐transition temperatures of the polyamides and poly(amide imide)s were 254–276 and 255–292 °C, respectively, and the imide‐containing poly(amide imide)s had better thermal stability than the polyamides. The polyamides showed higher transparency and were much lighter in color than the poly(amide imide)s, and their cutoff wave numbers were below 400 nm. In comparison with isomeric IXc–h, poly(amide imide)s VIIIc–h exhibited less coloring and showed lower yellowness indices. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3116–3129, 2004
Influence of substituents on the kinetics of epoxy/aromatic diamine resin systems
Authors: Liu Heping , Uhlherr Alfred , Varley Russell J. , Bannister Michael K.
Published: May 2004

Eleven different epoxy/diamine systems, including tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM), triglycidyl p‐aminophenol (TGAP), and diglycidyl ether of bisphenol A (DGEBA) with 4,4′‐diaminodiphenylsulfone (DDS), diethyltoluenediamine (DETDA), dimethylthiotoluenediamine (DMTDA), and meta‐phenylenediamine (m‐PDA), were studied with near‐infrared spectroscopy at different temperatures. The reactivities of the epoxies were determined and found to be in the following order when reacted with the same amine: DGEBA > TGAP > TGDDM. When the primary amine was reacted with the same epoxy, the order was DETDA > DDS > DMTDA; for the secondary amine, the order was DETDA > DMTDA > DDS. The relative reaction rates of the secondary amine to the primary amine were compared and discussed in terms of the structural differences and the corresponding substitution effect. It was concluded that the increase in the secondary amine reactivity of DETDA and DMTDA was caused by the deconjugation of the benzene‐ring π electrons from the lone pair on the N atom. The overall order of the secondary amine relative reactivity was DMTDA > DETDA > DDS for the same epoxy and TGDDM > TGAP > DGEBA for the same amine. The m‐PDA systems had no significant positive or negative substitution effects. Molecular orbital calculations were performed, and the results showed the most significant deconjugation effect in the secondary amine of DETDA. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3143–3156, 2004
First‐principle calculations for the active centers in vanadium‐containing chloroperoxidase and its functional models: Geometrical and spectral properties
Authors: Borowski Tomasz , Szczepanik Waldemar , Chruszcz Maksymilian , Brocławik Ewa
Published: May 2004

Vanadium‐containing haloperoxidases (VXPOs) constitute a group of relatively newly discovered metalloenzymes catalyzing oxidation of halogen anions to hypohalous acids by hydrogen peroxide. The structures of their native and peroxide‐bound forms as well as a reliable functional model system were characterized by X‐ray diffraction crystallography methods. In this work, we focus on two well‐characterized model systems and the active site itself of vanadium‐containing chloroperoxidase from Curvularia inaequalis (VCPO). For the two model systems, we performed geometry optimization and frequency calculations at the B3LYP/LanL2DZ level of theory. In addition, the vertical energies and oscillator strengths for a few lowest electronic transitions were computed with TDDFT. The solvent effect on electronic transitions was modeled either by means of a few explicit water molecules hydrogen‐bonded to studied complexes or by point charges representing them. As the active sites of VXPOs have to be modeled with additional charged groups of amino acids neutralizing the negative vanadium core, we restricted our calculations to DFT optimization and TDDFT calculations for excited states. In this paper, the results of these computations, namely, selected bond lengths and angles, vibrational frequencies, electronic transition energies, and oscillator strengths, are presented and compared with relevant literature data. This comparison, we believe, gives credits to the methodology and models used, which is also of importance for mechanistic considerations. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Sexual Abuse Prevention for Individuals with Mental Retardation: Considerations for Genetic Counselors
Authors: Levy Helen , Packman Wendy
Published: May 2004

It is now widely recognized that children, adolescents, and adults with mental retardation are especially vulnerable to sexual abuse. Because at least 10% of genetic conditions are reported to include mental retardation as a feature, the provision of services to individuals with mental retardation represents a substantial portion of the case load for many genetic counselors. Our objective is to educate genetic counselors and other health professionals about this vulnerable population in order to enhance the frequency and efficacy of inquiry into sexual education and sexual abuse prevention training for patients with mental retardation. The following review article is intended to assist genetic counselors by increasing their knowledge of factors that lead to sexual abuse and provides recommendations for integrating this information into the counseling interaction.
Erprobung eines Zeitverarbeitungstrainings bei Kindern mit Lese-Rechtschreibschwierigkeiten
Authors: Berwanger D. , von Suchodoletz W.
Published: May 2004

Zusammenfassung: Fragestellung: Ein Training der Zeitverarbeitung ist mittlerweile ein relativ weit verbreitetes Verfahren zur Behandlung von Störungen der Laut- und Schriftsprache, ohne dass dessen Wirksamkeit ausreichend belegt ist. In der vorliegenden Untersuchung wird der Frage nachgegangen, inwieweit ein Zeitverarbeitungstraining positive Auswirkungen auf Lese- und Rechtschreibleistungen ausübt. Methodik: In die Studie wurden 42 Kinder aus zwei 5. Klassen einer speziellen Schule zur Betreuung lese-rechtschreibschwacher Kinder einbezogen. Die Schüler der einen Klasse wurden der Trainingsgruppe (N = 21) und die der anderen der Kontrollgruppe (N = 21) zugeordnet. Das Training der Ordnungsschwelle (auditiv und visuell) und des Richtungshörens erfolgte über acht Wochen. Unmittelbar vor und nach der Behandlungsphase wurden bei allen Kindern neben Ordnungsschwelle und Richtungshören auch Lese- und Rechtschreibleistungen überprüft. Ein weiterer Retest wurde nach einem Zeitraum von sechs Monaten durchgeführt. Ergebnisse: Das Training führte zu einer deutlichen Verbesserung sowohl der visuellen als auch der auditiven Ordnungsschwelle. Hinsichtlich des Lesens und Rechtschreibens waren in der Therapiegruppe keine deutlicheren Fortschritte als in der Kontrollgruppe zu verzeichnen. Schlussfolgerung: Die Ergebnisse sprechen gegen spezifische Behandlungseffekte eines Zeitverarbeitungstrainings auf den Schriftspracherwerb. Es lassen sich zwar deutliche Verbesserungen der unmittelbar trainierten Leistungen, nicht jedoch Transfereffekte auf die Schriftsprache nachweisen. Ein Training von Ordnungsschwelle oder Richtungshören kann somit nicht zur LRS-Therapie empfohlen werden.
Driving mechanisms for >40 km of exhumation during contraction and extension in a continental arc, Cascades core, Washington
Authors: Paterson Scott R. , Miller Robert B. , Alsleben Helge , Whitney Donna L. , Valley Peter M. , Hurlow Hugh
Published: May 2004

In the NW North American Cordillera, the Cascades core region of the Coast Plutonic Complex underwent Late Cretaceous (>96 Ma to locally 73 Ma) SW‐NE contraction and crustal thickening followed by dextral transpression (∼73 to 55 Ma), then transtension (<55 Ma). Exhumation occurred during all three phases. During contraction, slow exhumation (∼0.6 mm/yr) occurred along the margins of the core, driven by isostatic rebound and erosion, and faster exhumation (>3 mm/yr) by local thrusting in regions undergoing crustal thickening. In the central part of the core (Chelan block), >40 km of exhumation occurred between 91 and 45 Ma, about half of which occurred during early contraction (driven by thrusting) and half during top‐to‐north, arc‐oblique shear during reactivation of a midcrustal Cretaceous thrust, the Dinkelman decollement. The footwall of this thrust consists of the Swakane Biotite Gneiss, a Cretaceous, metaclastic assemblage with recorded pressures of 10–12 kbar, no arc‐related magmatism, and structures dominated by pervasive top‐to‐north shearing. The hanging wall consists of the Napeequa Complex, an oceanic assemblage with recorded pressures of 6–12 kbar, voluminous arc‐related magmatism, and complex structures indicating early top‐to‐WSW shearing, younger top‐to‐north shearing, and widespread folding. In the Napeequa, top‐to‐north shearing started by 73 Ma during melt‐present conditions at pressures ≥6 kbar. Top‐to‐north shearing in both hanging wall and footwall continued during exhumation (∼1.6 mm/yr) and cooling to greenschist facies conditions during which slip became increasingly localized, eventually resulting in formation of pseudotachylite on discrete slip surfaces. We suggest that arc‐oblique extension was driven by along‐arc heterogeneity in displacements/erosion, initially during transpression and underplating of continental sediments, and later during transtension.
Planktonic foraminiferal δ13C records from Southern Ocean sediment traps: New estimates of the oceanic Suess effect
Authors: King Alexandra L. , Howard William R.
Published: May 2004

The carbon isotopic composition is measured for three species of planktonic foraminifera (Globigerina bulloides, Globorotalia inflata and Neogloboquadrina pachyderma (s.)) from Southern Ocean sediment traps. The sediment traps represent the annual flux of foraminifera in Subtropical to Polar Frontal environments from the western Pacific/Southern Australia sector. Comparison between the seasonal δ13C composition of the foraminifera and estimated δ13C of dissolved inorganic carbon (DIC) allows disequilibrium effects to be determined. Disequilibrium exhibits a latitudinal trend, with greatest offsets from equilibrium at lower latitudes. This effect causes a north to south increase in foraminiferal δ13C, while the δ13CDIC displays a decrease across these latitudes. Disequilibrium in G. bulloides can be accounted for by changes in temperature. The relationship between disequilibrium and temperature which we derive in this field study is consistent with the laboratory relationship of Bemis et al. [2000]. Corrected δ13C for G. bulloides is closely correlated to seasonal changes in nutrients at each site, indicating the utility of G. bulloides δ13C as a nutrient tracer in Southern Ocean environments. Comparison between flux‐weighted sediment trap values and nearby core tops indicates a modern depletion in δ13C, which we attribute to the oceanic Suess effect. The imprint of this effect on the foraminiferal isotopes provides further evidence for the equilibration between surface waters and the atmosphere in the Subantarctic Zone.
Barotropic and baroclinic tidal currents on the Mackenzie shelf break in the southeastern Beaufort Sea
Authors: Kulikov Evgueni A. , Rabinovich Alexander B. , Carmack Eddy C.
Published: May 2004

Tidal currents near the outer shelf break of the Mackenzie Shelf in the southern Beaufort Sea were examined using year‐long (1987–1988) current measurements from the upper (∼35 m) and lower (∼150 m) layers at four sites along the southeast (SS1), northeast (SS2), north central (SS3), and northwest (SS4) perimeter of the shelf. At all stations, semidiurnal currents were dominant, and upper layer currents were approximately double those observed in the lower layer. Maximum M2 currents were observed above the sharp northeastern corner of the Mackenzie Shelf (6.0–7.5 cm·s−1), while in the Mackenzie Canyon they were negligible. Diurnal currents were weaker and depth uniform; maximum K1 currents (1.5–3.0 cm·s−1) were found in the eastern part of the shelf. Diurnal and lower layer semidiurnal currents were in good agreement with those computed numerically by Kowalik and Proshutinsky [1994], indicating that these currents are essentially barotropic. In contrast, upper layer semidiurnal currents were mainly baroclinic. About 74% of the total energy of semidiurnal currents was associated with baroclinic coherent (phase‐locked) tidal currents, while barotropic (12%), baroclinic incoherent (7%), and inertial (7%) components are the remaining semidiurnal currents in this area. High baroclinic generation coefficients (the ratio of locally generated baroclinic waves to barotropic waves) for stations SS2 and SS3 (about 7.0–8.0 in comparison with 0.3 for SS1 and SS4) located near the northeastern Mackenzie Shelf identify this region as a probable generation source of intensive internal tidal waves, which become then locally resonantly trapped between the shelf and the critical latitudes.
Detection and attribution of changes in 20th century land precipitation
Authors: Lambert F. Hugo , Stott Peter A. , Allen Myles R. , Palmer Michael A.
Published: May 2004

Observed globally‐averaged land precipitation changes over the 20th century are compared with simulations of the HadCM3 climate model using an “optimal fingerprinting” method. We find that observed changes in precipitation are too large to be consistent with model‐generated internal variability and are consistent with (attributable to) the combination of natural and anthropogenic forcings applied to the model. By comparing precipitation observations to shortwave and longwave forcing timeseries, we find that most of the forced variation in precipitation appears to be driven by natural shortwave forcings. We are unable to detect a response to anthropogenic longwave forcings in isolation. Finally, we seek to explain these results in terms of perturbations to the energy budget of the troposphere.
Solar irradiance variability during the October 2003 solar storm period
Authors: Woods Thomas N. , Eparvier Francis G. , Fontenla Juan , Harder Jerald , Kopp Greg , McClintock William E. , Rottman Gary , Smiley Byron , Snow Martin
Published: May 2004

The extraordinary solar storms between 18 October 2003 and 5 November 2003 include over 140 flares, primarily from two different large sunspot groups. There were 11 large X‐class flares during this period, including an X17 flare on 28 October 2003 and an X28 flare on 4 November 2003. The X28 flare is the largest flare since GOES began its solar X‐ray measurements in 1976. The solar (full‐disk) irradiance during these flares was observed by the instruments aboard the NASA Solar Radiation and Climate Experiment (SORCE) spacecraft and the NASA Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED) spacecraft. The total solar irradiance (TSI) dropped by unprecedented 0.34% during this period due to the dark, large sunspots. In addition, the TSI increased by 270 ppm during the X17 (4B optical) flare on 28 October, the first definitive measurement of a TSI flare event. The ultraviolet (UV) variations for this X17 flare range from a factor of about 50 shortward of 10 nm to about 10% for the Mg II 280 nm emission. One interesting result for the UV flare variations is that the broad wings of the H I Lyman‐α (121.6 nm) emission increased by more than a factor of 2 during the X17 flare while the core of the Lyman‐α emission only increased by 20%. Another interesting result is the time profile of the Si III 120.6 nm emission, which shows a sharp 1‐minute long increase by a factor of 17 during the impulsive phase.
Dynamic rupture process of the 1999 Chi‐Chi, Taiwan, earthquake
Authors: Zhang Wenbo , Iwata Tomotaka , Irikura Kojiro , Pitarka Arben , Sekiguchi Haruko
Published: May 2004

The dynamic rupture process of the Chi‐Chi earthquake has been investigated based on a 3‐D spontaneous shear crack model, using a thick fault zone model and a slip‐weakening friction law. Our results show that the dynamic rupture process of this event is very complex. The distribution of the rupture starting time is much more inhomogeneous than that of the kinematic model. We find that the zones with a large strength excess on the fault surface delay the rupture propagation. The rupture front jumps from the zones with high strength excess to the near zones with low strength excess when encounters the zones with high strength excess, leaving the unbroken zones behind which subsequently rupture. We also found that the motion on the hanging‐wall side is larger than that on the foot‐wall side.
Spatial Mismatch outside of Large Urban Areas: An Analysis of Welfare Recipients in Fresno County, California
Authors: Blumenberg Evelyn , Shiki Kimiko
Published: May 2004

Numerous scholars assert that welfare recipients face a mismatch between their residential locations in inner-city or rural areas and employment opportunities located in the suburbs far from where they live. However, the authors' findings bring into question the wholesale application of the spatial mismatch hypothesis to all welfare recipients. Welfare recipients in mid-sized cities such as Fresno, California, do not face spatial barriers to employment as they live in compact areas where distances between residential and employment locations are relatively short. In contrast, job access is important in the nonurbanized areas of Fresno County where welfare recipients who live in job-rich neighborhoods are more likely to be employed than are recipients who are dispersed throughout more isolated, nonurbanized areas.
Local Government and the Changing Institutional Landscape of Economic Development in England and Wales
Authors: Fuller Crispian , Bennett Robert J , Ramsden Mark
Published: May 2004

This paper assesses the response by local authorities to the new institutional structure introduced in England and Wales since 1997: of Regional Development Agencies (RDAs), the Welsh Assembly and Welsh Development Agency (WDA), subregional partnerships, the Learning and Skills Council (LSC), Education and Learning Wales (ELWa), and local government new well-being and Best Value initiatives. The paper demonstrates, using new survey evidence, that RDAs are beginning to promote a regional framework for local organizations, but the strategic impact is limited to county, unitary, and metropolitan areas, which are focused heavily on programme delivery. More generally, regional strategy inputs have added yet another dimension to local government partnerships. RDAs are not yet, therefore, the strategic bodies for all areas that was originally planned. Regional Chambers and the Welsh Assembly have weak influence on local government and are not yet effective monitoring bodies on the RDAs/WDA. Subregional partnerships offer potential for regional-local government strategy, but are chiefly involved in programme design (especially for regeneration) and their future importance appears limited. The transfer from TECs to the LSC/ELWa has had much less impact than expected: local government was already leader and financier of most of the projects in which TECs were involved. However, a reduction in level of activity, effectiveness, and resources has occurred for most projects in England, though to a lesser extent in Wales. Overall, the paper demonstrates that as yet changes in institutions have produced little real changes in how economic development occurs or how local government operates. The complexity and fragmentation of economic development institutions by government, on balance, appear to have increased rather than diminished.
The Depiction of Car Light Beams in a Child Born Completely Blind
Authors: D'Angiulli Amedeo , Maggi Stefania
Published: May 2004

A 12-year-old child (DI) who was completely blind from birth, made a series of tactual (raised-lines) drawings of cars. Among them, there was the depiction of a ‘fast car at night’ in which DI drew beams of light projecting out of the car. We analyse this drawing, and the preceding ones. We argue that the way in which cars and light beams were depicted by DI cannot be fully and solely explained by graphic imprecision, executive or motor deficiencies, or by rote or verbal learning. Instead, we propose that the most plausible explanation is that DI's depiction of light in a fast car at night reflects the child's naive knowledge of light propagation, and that this knowledge was gained through perceiving light as radiant heat.
The Spatial and Temporal Conditions for Perceiving Velocity as Constant
Authors: Tayama Tadayuki
Published: May 2004

Perceived velocities during a brief period of exposure (<1.2 s) were measured to examine how much time is necessary to perceive velocity as constant. Moving sinusoidal gratings were used as stimuli at relatively low velocities. At the beginning of each stimulus presentation, a moving pattern was perceived as stationary until a critical time had passed. After that, perceived velocity was positively correlated with moving distance, irrespective of physical velocity below a critical moving distance. Beyond the critical moving distance, velocity was perceived as constant. A simple model is presented to explain these results.