bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study on E-government Service Quality and Effectiveness of E-government Services in Selected Divisional Secretariats
Authors: Sarangan Balachandran , Sarangan Rishaana
Published: February 2023

Acknowledge to the rapid global growth of internet and information technology, many governments around the world have transformed their services from traditional services to electronic means. Using the internet, nowadays governments are offering more convenient and faster access to their services and information. This has been achieved by the use of e-government services. Even though, the concept of e-government is still in its early stage, it has become an important issue in recent years. The main purpose of introducing e-government services is to effective services to the citizens. However, many governments have been developing the e-government services without paying full attention to the effectiveness of the e-government services and the requirements of citizens. Accordingly, the main purpose of this study is to identify the relationship between e-government service quality and effectiveness of e-government services. This study conducted based on quantitative method and the primary data collected through the structured questionnaires. In total, 112 questionnaires were distributed to citizens who accessed e-government services in 14 divisional secretariats in Batticaloa District. From that, total of 100 completed questionnaires were gathered, representing 89.26% response rate. The collected data was analyzed with the aid of SPSS (22.0) software. The data analysis method is specially focused on the bivariate and multi variate analysis due to the specific research questions. Major findings indicates that there is a positive significant relationship between all the dimensions of e-government service quality and effectiveness of e-government services. Further simple regression analysis between e-government service quality and effectiveness of e-government service results also explicit e-government service quality has a positive significant influence on effectiveness of e-government services. The results of this study will assist the government entities in proper development and implementation of e-government services in the divisional secretariats to provide quality e-government services to the citizens. Future research can cover local e-government projects in national level.
Differential regulation of G protein α‐subunit GTPase activity by peptides derived from the third cytoplasmic loop of the α2‐adrenergic receptor
Authors: Wagner Thomas , Oppi Cristina , Tocchini Valentini Glauco P.
Published: July 2002

The effect of peptides homologous to segments of a G protein‐coupled receptor on the GTPase activity of recombinant G0α (rGoα) and G,a (rGsα) has been tested. These peptides contain overlapping sequences spanning from amino acid 212 of the putative fifth transmembrane domain to amino acid 229 of the third cytoplasmic loop of the a2 adrenergic receptor. Interestingly, two peptides (comprising residues 212–227 and 214–227) strongly inhibit the basal GTPase activity of both rGoα and rGsα. Instead, a C‐terminally extended peptide (residues 216–229) stimulates rGoα but slightly inhibits rGsα. Circular dichroism spectroscopy of the peptides reveals that an a helical structure is more easily inducible in the inhibitory ones. These findings constitute an example of peptides representing cytoplasmic receptor sequences that differentially modulate the GTPase activity of recombinant G protein α‐subunits.
Human influenza virus recognition of sialyloligosaccharides
Authors: Gambaryan A.S. , Piskarev V.E. , Yamskov I.A. , Sakharov A.M. , Tuzikov A.B. , Bovin N.V. , Nifant'ev N.E. , Matrosovich M.N.
Published: July 2002

Sialic acids are essential components of cell‐surface receptors utilized by influenza viruses. To evaluate the recognition of asialic sugar parts of the receptor, three representative strains of human influenza A and B viruses were tested for their binding of a panel of sialyloligosaccharides. The highest affinity binding carbohydrate determinants recognized by the viruses in a context of different core structures were Neu5Acα2‐3Gal for the type B virus, Neu5Acα2‐6Gal for the H3 subtype virus, and Neu5Acα2‐6Ga/β1‐4GlcNAc for the H1 subtype virus. Penultimate to these determinants parts of sialyloligosaccharides studied either contributed less significantly to the binding affinity, or interfered with the binding.
An empirical analysis of the equity markets in China
Authors: Mookerjee Rajen , Yu Qiao
Published: July 2002

This paper subjects the newly established stock markets in Shanghai and Shenzhen to tests of market efficiency, utilizing daily stock price data. Using a battery of tests, the study concludes that there are significant inefficiencies present on both exchanges. These can be traced to the unique structural and institutional problems that plague both exchanges. The study also tests for the presence of seasonal anomalies on both exchanges. The results show that there are significant negative weekend and positive holiday effects, but there is no evidence of a January effect or early January effect.
Comparative effects of levosulpiride and cisapride on gastric emptying and symptoms in patients with functional dyspepsia and gastroparesis
Authors: Mansi C. , Borro P. , Giacomini M. , Biagini R. , Mele M. R. , Pandolfo N. , Savarino V.
Published: July 2002

Background:

The efficacy of several prokinetic drugs on dyspeptic symptoms and on gastric emptying rates are well‐established in patients with functional dyspepsia, but formal studies comparing different prokinetic drugs are lacking.

Aim:

To compare the effects of chronic oral administration of cisapride and levosulpiride in patients with functional dyspepsia and delayed gastric emptying.

Methods:

In a double‐blind crossover comparison, the effects of a 4‐week administration of levosulpiride (25 mg t.d.s.) and cisapride (10 mg t.d.s.) on the gastric emptying rate and on symptoms were evaluated in 30 dyspeptic patients with functional gastroparesis. At the beginning of the study and after levosulpiride or cisapride treatment, the gastric emptying time of a standard meal was measured by 13C‐octanoic acid breath test. Gastrointestinal symptom scores were also evaluated.

Results:

The efficacy of levosulpiride was similar to that of cisapride in significantly shortening (P < 0.001) the t1/2 of gastric emptying. No significant differences were observed between the two treatments with regards to improvements in total symptom scores. However, levosulpiride was significantly more effective (P < 0.01) than cisapride in improving the impact of symptoms on the patients’ every‐day activities and in improving individual symptoms such as nausea, vomiting and early postprandial satiety.

Conclusion:

The efficacy of levosulpiride and cisapride in reducing gastric emptying times with no relevant side‐effects is similar. The impact of symptoms on patients’ everyday activities and the improvement of some symptoms such as nausea, vomiting and early satiety was more evident with levosulpiride than cisapride.
Tolterodine: A Safe and Effective Treatment for Older Patients with Overactive Bladder
Authors: Malone‐Lee James G. , Walsh J. Bernard , Maugourd Marie‐France , The Tolterodine in the Elderly Study Group
Published: July 2002

OBJECTIVE: To investigate the clinical safety and efficacy of two dosages of tolterodine in older patients with symptoms attributable to overactive bladder.

DESIGN: Randomized, double‐blind, placebo‐controlled, parallel‐group, multinational, phase III study.

SETTING: Incontinence, older care, urological, and urogynecological clinics in the United Kingdom, France, and the Republic of Ireland.

PARTICIPANTS: One hundred and seventy‐seven older patients (age ≥65 years) with symptoms of urinary urgency, increased frequency of micturition (≥8 micturitions/24 hours), and/or urge incontinence (≥1 episode/24 hours).

INTERVENTION: Tolterodine 1 mg or 2 mg twice daily (bid), or placebo, for 4 weeks.

MEASUREMENTS: Safety and tolerability were evaluated through spontaneously reported adverse events, electrocardiogram, and blood pressure measurements. Efficacy was assessed using micturition diary variables: mean change from baseline in frequency of micturition and number of incontinence episodes/24 hours.

RESULTS: The mean age of the patient population was 75 years. Overall, ≥87% of patients completed the study. Neither dosage of tolterodine was associated with serious drug‐related adverse events during the study. No cardiac arrythmogenic events were noted. Dry mouth (mild to moderate intensity) was the most common adverse event in both the placebo and tolterodine treatment groups. Three percent of patients in the tolterodine 2 mg bid group discontinued treatment because of dry mouth, compared with 2% of placebo‐treated patients. Compared with placebo, statistically significant decreases in micturition frequency were apparent in both tolterodine treatment groups. Furthermore, patients treated with tolterodine 2 mg bid had statistically significant decreases in urge incontinence episodes/24 hours and increases in volume voided per micturition compared with placebo.

CONCLUSION: Tolterodine (taken for 4 weeks) is safe and shows efficacy, particularly at a dosage of 2 mg bid, in the treatment of older patients with urinary symptoms attributable to overactive bladder. J Am Geriatr Soc 49:700–705, 2001.
Band-gap determination by photoreflectance of InGaAs and InAlAs lattice matched to InP
Authors: Gaskill D. K. , Bottka N. , Aina L. , Mattingly M.
Published: July 2002

Photoreflectance-derived band-gap parameters as a function of temperature for InGaAs and InAlAs lattice matched to InP are reported. The experiment was performed on a set of samples of various compositions (and strains) yielding greater reliability and ensuring self-consistency. For InGaAs, fits to the Varshni equation gave E0(T=0 K)=803 meV, α=4.0×10−4 eV K−1, and β=226 K. For InAlAs, E0(T=0 K)=1.541 eV, α=4.7×10−4 eV K−1, β=149 K, and Δ0=338 meV.
Equilibrium critical thickness for Si1−xGex strained layers on (100) Si
Authors: Houghton D. C. , Gibbings C. J. , Tuppen C. G. , Lyons M. H. , Halliwell M. A. G.
Published: July 2002

The critical thickness for Si1−xGex strained layers for the alloy range 0<x<0.15 has been determined from annealed epilayers using mapping techniques which allow single dislocation detection and composition thickness measurements over large areas (∼50 cm2 ). A series of Si1−xGex layers was deposited by molecular beam epitaxy in which the composition (x) and thickness (h) were continuously varied across the substrate to produce a slowly changing strain energy density through the stable/metastable transition. On annealing at either 750 or 900 °C for 30 min, an abrupt transition in relaxation behavior was found at critical values of thickness and composition (hc,xc ). Increasing the anneal temperature or time did not shift the transition giving identical (hc,xc ) values. At strain thicknesses above these critical values a large increase in defect density was observed (>∼104 , cm−2) whereas in thinner strained epilayers, below the thermodynamic stability curve, no misfit dislocations were found. Nomarski microscopy of defect etched surfaces and x-ray topography were used to reveal misfit dislocations formed during the initial stages of relaxation. The appearance of single misfit dislocations at a density ≊1 cm−2 was taken as the criterion for a ‘‘relaxed’’ layer. The critical strain and thickness in the vicinity of these transition points were determined on the as-grown wafer by x-ray diffraction and Rutherford backscattering spectrometry with confirmation of layer thicknesses by cross-sectional transmission electron microscopy. The Matthews–Blakeslee [J. Cryst. Growth 27, 118 (1974)] equilibrium critical thickness he (nm), vs Ge atom fraction curve given by xe =0.55/he  ln(4he /b) for 1/2 a0〈110〉, 60° glide dislocations with a Burgers vector b ∼0.4 nm, is an excellent fit to these experimental data, i.e., xc =xe and hc =he .
Noise in the Coulomb blockade electrometer
Authors: Zimmerli G. , Eiles T. M. , Kautz R. L. , Martinis John M.
Published: July 2002

We have measured the noise of a Coulomb blockade electrometer. Below 100 Hz, the noise referred to the input charge has a 1/f power spectrum with a charge noise of 3×10−4 e/√Hz and an energy sensitivity EN of 3×104 ℏ at 10 Hz. The 1/f noise probably results from the stochastic occupation of charge traps which could in principle be eliminated. The theoretical noise floor is set by shot noise, and indirect measurements show that this contribution to EN can be as small as 1.5 ℏ, suggesting that the electrometer will be a quantum limited amplifier if the 1/f noise can be eliminated.
Preparation of coiled carbon fibers by pyrolysis of acetylene using a Ni catalyst and sulfur or phosphorus compound impurity
Authors: Motojima S. , Hasegawa I. , Kagiya S. , Momiyama M. , Kawaguchi M. , Iwanaga H.
Published: July 2002

Coiled carbon fibers were prepared by pyrolysis of acetylene activated using a Ni catalyst and a small amount of impurities at 600–800 °C. It was found that the addition of a small amount of sulfur or phosphorus compound impurities in acetylene was indispensable for the growth of coiled carbon fibers. Among the sulfur compounds used, thiophene was the most effective for growing coiled carbon fibers with uniform coil diameter and producing a high yield (about 50% coils). Similar results were obtained with phosphorus trichloride.
Enhanced methyl-radical production in an Ar-CH4 pin-hollow cathode discharge
Authors: Iizuka S. , Takada T. , Sato N.
Published: July 2002

A methyl-radical formation is observed to be enhanced in an Ar-CH4 discharge plasma using a hollow cathode with movable pins inside. In the discharge with pins, high energy electrons in the radial edge region of the plasma column produce methyl radicals. They diffuse toward the central region of the plasma column, increasing their density, where the electron temperature is so low (≂0.4 eV) that there occurs no reaction to decrease the methyl-radical density.
Circular dichroism measurements. I. Calibration of a circular dichroism spectrometer
Authors: Shindo Yohji , Nakagawa Masayuki
Published: July 2002

The Mueller matrix approach is used to analyze the problems associated with the calibration of a modern CD spectropolarimeter constructed on the basis of a modulation technique in polarization spectroscopy. As a result, the performance of the CD spectropolarimeter is found to be determined by the characteristics of the photomultiplier as a partial polarizer, the residual static strain birefringence of the modulator, and the first harmonic response of a lock-in amplifier. Furthermore, the CD signal is greatly affected by the circular birefringence of a sample in addition to the above three factors. Thus, the necessity of checking these factors before the calibration is carried out using a standard sample is pointed out.
Picosecond time-resolved circular dichroism spectroscopy: experimental details and applications
Authors: Xie Xiaoliang , Simon John D.
Published: July 2002

An experimental apparatus for measuring time-resolved circular dichroism (CD) with picosecond resolution is described. The time resolution of the device is determined by the laser pulse width, not the modulation frequency of an electro-optic or piezo-optic crystal as is the case for commercial CD spectrometers. The time-dependent CD signal can be monitored over the wavelength range from 280 to 850 nm. The data from single wavelength studies can be pieced together to generate time dependent spectra. The experimental approach is compared to previous time-resolved CD techniques which, for technical reasons, have been limited to, at most, nanosecond resolution. The picosecond apparatus is shown to be free of many of the polarization artifacts present in these previous devices. The utility of this technique is demonstrated by examining result on the time dependent near-UV CD of myoglobin following the photoelimination of coordinated CO from carbonmonoxymyoglobin.
A conceptual model for ray tracing calculations with mosaic crystals
Authors: Sánchez del Río M. , Bernstorff S. , Savoia A. , Cerrina F.
Published: July 2002

Mosaic crystals provide an interesting choice for synchrotron radiation monochromators under certain conditions. They show a wider and lower reflectivity curve than perfect crystals, but a higher integrated reflectivity. Some mosaic crystals such as graphite or beryllium could be considered as monochromators or premonochromators for third generation synchrotron radiation machines (Sincrotrone Trieste, European Synchrotron Radiation facility, etc.). In order to assess these possibilities, we have implemented a new mosaic crystal part in the ray tracing code SHADOW. The effect of the random distribution of the crystallites in a mosaic crystal can be analyzed efficiently with a Monte Carlo method. Taking into account the random distribution of the crystal planes, modeled as a Gaussian of standard deviation κ, it is possible to reproduce the well known focusing and defocusing properties of these crystals. For reflectivity calculations we have implemented in the computer code the Mosaic Crystals Theory of Zachariasen. As secondary extinction is not negligible in mosaic crystals, we have also included the penetration effect of the x-ray beam inside the crystal.
Integrated cryogenic scanning tunneling microscopy and sample preparation system
Authors: Tessmer S. H. , Harlingen D. J. Van , Lyding J. W.
Published: July 2002

A scanning tunneling microscope (STM) operable from room temperature to 1.5 K with an integrated sample preparation chamber has been constructed and successfully tested. Both the sample and the tunneling tip can be cleaned and/or modified in a UHV processing chamber which is connected at the top of a liquid-helium flow cryostat. The STM is mounted to a threaded rod inside the cryostat so that it can be translated vertically. This allows a newly prepared sample/tip to be transferred onto the STM and lowered into a cryogenic environment without breaking vacuum, minimizing surface contamination which causes significant tunneling problems at cryogenic temperatures.
Optical limiting effect in a two-photon absorption dye doped solid matrix
Authors: He Guang S. , Bhawalkar Jayant D. , Zhao Chan F. , Prasad Paras N.
Published: July 2002

We recently reported a new lasing dye, trans-4-[p-(N-ethyl-N-hydroxylethylamino)styryl]-N-methylpyridinium tetraphenylborate (ASPT), which has also been shown to possess a strong two-photon absorption (TPA) and subsequent frequency upconversion fluorescence behavior when excited with near infrared laser radiation. Based on the TPA mechanism, a highly efficient optical limiting performance has been demonstrated in a 2 cm long ASPT-doped epoxy rod pumped with 1.06 μm Q-switched laser pulses at 50–250 MW/cm2 intensity levels. The measured nonlinear absorption coefficient reached 6 cm/GW for the tested sample of dopant concentration d0=4×10−3 M/L. The molecular TPA cross section of ASPT in the epoxy matrix is estimated as σ2=2.5×10−18 cm4/GW or σ2′=4.7×10−46 cm4/photon/s, respectively. Two-photon pumped cavity lasing is also observed in an ASPT-doped polymer rod.
Nitrogen donors and deep levels in high-quality 4H–SiC epilayers grown by chemical vapor deposition
Authors: Kimoto T. , Itoh A. , Matsunami H. , Sridhara S. , Clemen L. L. , Devaty R. P. , Choyke W. J. , Dalibor T. , Peppermüller C. , Pensl G.
Published: July 2002

4H-SiC epilayers grown by chemical vapor deposition were characterized by Hall effect, admittance spectroscopy, low-temperature photoluminescence, and deep level transient spectroscopy (DLTS). The nitrogen (N) donor activation energies were estimated as 45–65 meV at hexagonal and 105–125 meV at cubic sites from Hall effect investigations in agreement with the data taken by admittance spectroscopy. In low-temperature photoluminescence, the N bound exciton peaks were dominant, however, free exciton peaks were also observed. DLTS measurements revealed a low concentration of electron traps (∼1013cm−3) for both samples grown on Si and C faces, indicating high-quality epilayers independent of the substrate polarity.
Selected contactless optoelectronic measurements for electronic applications (invited)
Authors: Cutolo Antonello
Published: July 2002

The area of contactless characterization techniques for electronic applications is too wide a topic to be considered in full detail inside a single review article. On this line of argument, we considered only some contactless optoelectronic techniques paying particular attention to those optoelectronic techniques which can be easily employed for material diagnostics or to perform simple voltage or temperature measurements in electronic devices. In spite of their simplicity and reliability, some of these techniques are not well known by the electronic community. The considered techniques include: scanning electron, photoexcitation and force microscope, electro-optical sampling techniques, charge sensing probes, second harmonic generation, and photoacoustic and thermal wave microscopy. Applications to signal processing, detection and measurement of microcracks, temperature, lifetime, surface recombination velocity, diffusivity, and injection level are discussed. The article is, then, completed by a very rich bibliography and by three appendices describing some physical phenomena (electro-optic, plasma optic, and photoacoustic effect) instrumental for understanding most of the considered techniques. Most of the considered techniques can be mounted in almost each laboratory as they do not require particularly expensive and bulky instrumentation.
Optimizing power extraction in stretched-pulse fiber ring lasers
Authors: Tamura K. , Nakazawa M.
Published: July 2002

A variable output coupling scheme is described for a stretched-pulse polarization additive pulse mode-locked (APM) fiber ring laser. The scheme allows the coupling percentage to be changed while the laser is running and allows for the maximum possible power extraction before cavity losses inhibit mode-locked operation. We describe how the nonlinear pulse dynamics change to compensate the change in cavity loss. Compared to high power output coupling schemes that use the APM rejection port, this method provides cleaner output pulses at comparable output powers. Pulse energies of 0.39 nJ are obtained at 48% output coupling in a diode-pumped system. 88 fs pulses with time-bandwidth products of 0.49 are obtained after output chirp compensation using a silicon prism pair.
Long-wavelength InAsSb photoconductors operated at near room temperatures (200–300 K)
Authors: Kim J. D. , Wu D. , Wojkowski J. , Piotrowski J. , Xu J. , Razeghi M.
Published: July 2002

Long-wavelength InAs1−xSbx photoconductors operated without cryogenic cooling are reported. The devices are based on p-InAs1−xSbx/p-InSb heterostructures grown on (100) semi-insulating GaAs substrates by low pressure metalorganic chemical vapor deposition (LP-MOCVD). Photoreponse up to 14 μm has been obtained in a sample with x=0.77 at 300 K, which is in good agreement with the measured infrared absorption spectra. The corresponding effective lifetime of ≊0.14 ns at 300 K has been derived from stationary photoconductivity. The Johnson noise limited detectivity at λ=10.6 μm is estimated to be about 3.27×107 cm Hz1/2/W at 300 K.
Room-temperature repositioning of individual C60 molecules at Cu steps: Operation of a molecular counting device
Authors: Cuberes M. T. , Schlittler R. R. , Gimzewski J. K.
Published: July 2002

C60 molecules absorbed on a monoatomic Cu step have been reversibly repositioned at room temperature with the tip of a scanning tunneling microscope by performing controlled displacements along the step direction. We demonstrate the feasibility of building an abacus on the nanometer scale using single molecules as ‘‘counters,’’ Cu monoatomic steps as ‘‘rods’’ that constrain the molecular motion to one dimension, and the scanning tunneling microscope as an ‘‘actuator’’ for counting operations.
Laser-induced coloration of WO3
Authors: Zhao Y. , Feng Z. C. , Liang Y. , Sheng H. W.
Published: July 2002

It has long been recognized that WO3 can be colored through electro-, photo-, and thermo-chromism processes. We report here that WO3 turned to a deep blue color upon just one pulse irradiation of the XeCl excimer laser (λ=308 nm, pulse duration=36 ns, output energy=100 mJ/pulse). Scanning electron microscopy (SEM) images showed that a melted layer was formed on the surface of the sample. The color change was demonstrated by UV-visible diffuse reflectance. X-ray photoelectron spectroscopy (XPS) showed the partial reduction of WO3 and the appearance of conduction band electrons. Calorimetry measurement results indicated that reoxidation happened at 400–440 °C in air. From these experimental results combining with the calculation, it was concluded that the laser-induced coloration is different from ordinary photochromism induced by UV light, and may be attributed to thermochromism.
Nearly noise-free transistor operated in the 2–18 GHz range
Authors: Fendrich J. A. , Feng M.
Published: July 2002

Temperature dependent measurements of the noise parameters of a pseudomorphic high electron mobility transistor show the minimum noise figure vanishes at low temperatures for frequencies from 2 GHz up to 18 GHz and for most currents. We propose that the exponential decrease seen in the noise figure with temperature is due to a reduction of thermally activated noise sources with an activation energy of ∼95 meV. Other noise-parameter data suggest a flattening of the noise figure paraboloid as temperature is decreased. These results demonstrate the feasibility of designing a near 0.1 dB noise figure amplifier for high-frequency operation over a wide range of currents.
Discrimination between bulk and interface scenarios for the suppression of the switchable polarization (fatigue) in Pb(Zr,Ti)O3 thin films capacitors with Pt electrodes
Authors: Colla E. L. , Taylor D. V. , Tagantsev A. K. , Setter N.
Published: July 2002

A simple and reliable method which allows one to distinguish between the two major microscopic scenarios for the suppression of the switching polarization (Prs), i.e., pinning of ferroelectric domain walls (DWs) through the Pb(Zr,Ti)O3 film (PZT) (bulk scenario) and inhibition of the growth of opposite domains due to the nucleus suppression at the electrode interfaces (interface scenario), is proposed. In addition, a new electric treatment able to significantly suppress Prs in Pt–PZT–Pt ferroelectric capacitors (FECAPs) of thicknesses above 1.4 μm, was discovered and studied. It consists of the application of an external alternating electric field (Ee) which cycles the polarization at very low frequency (1.7 mHz). After only 10–20 cycles, Prs can be suppressed by a factor of 10. The same FECAP, when subjected to Ee at higher frequency (30 kHz), endures at least 108 switches, before attaining an equivalent Prs suppression (hereafter called fatigue). The fatigued states obtained with the two different procedures appear to be different. In the first case (slow cycling) it is suggested that the suppression of Prs is related to the DW pinning scenario, whereas in the second case—which corresponds to the normal fatiguing procedure—it is related to the interface scenario.
Dielectric properties of epitaxial BaTiO3 thin films
Authors: Hoerman B. H. , Ford G. M. , Kaufmann L. D. , Wessels B. W.
Published: July 2002

The dielectric response of epitaxial BaTiO3 thin films deposited on MgO was measured through surface electrodes as a function of applied bias, frequency, and temperature. The room temperature value of the dielectric constant was ∼500 with a dissipation factor, tan(δ), of 0.05 at 100 kHz. Measurements varying the bias field showed hysteresis of the dielectric response and a tunability of 30% for a maximum applied field of ∼7 MV/m. The frequency response of the dielectric constant is well described by a Curie–von Schweidler power law with an exponent ∼0.04 in the range 1 kHz–13 MHz. The films undergo a diffuse phase transition at temperatures higher than the bulk Curie temperature. The behavior of the dielectric response is attributed to the presence of residual strain in the epitaxial thin films.
GaN heteroepitaxial growth on silicon nitride buffer layers formed on Si (111) surfaces by plasma-assisted molecular beam epitaxy
Authors: Nakada Yoshinobu , Aksenov Igor , Okumura Hajime
Published: July 2002

Wurtzite GaN films were grown on silicon nitride buffer layers formed on Si (111) substrates by radio frequency plasma-assisted molecular beam epitaxy. Reflection high energy electron diffraction, Auger electron spectroscopy, transmission electron microscopy, and photoluminescence results indicate that the single crystalline wurtzite GaN was grown on the buffer layers of amorphouslike silicon nitride formed on Si (111) substrates by taking the following relationship with the substrate: GaN [0001]//Si [111] and GaN (1̄1̄20)//Si (11̄0). Both faces of the silicon nitride buffer layer were found to be flat and sharp, the thickness of the buffer layer (1–1.5 nm) being constant across the interface. Efficient bound exciton emission was observed at 3.46 eV. The growth technique described was found to be simple but very powerful for growing high quality GaN films on Si substrates.
Structural relaxation enhanced by Cl ions in silica glass
Authors: Saito K. , Ikushima A. J.
Published: July 2002

The effect of Cl ions on the structural relaxation in silica glass was investigated by observing the fictive temperature, which was determined from the position of infrared absorption peak around 2260 cm−1 related to the average Si–O–Si bond angle. It has been found that Cl ions reduce the relaxation time of the long-range cooperative relaxation due to viscous flow, the so-called α relaxation. Moreover, Cl ions reduce the relaxation time of a subrelaxational process, caused by local structural relaxation. Although Cl has been used in industry only for dehydrating silica glass for optical fibers, these structural relaxation enhanced by Cl may be used advantageously to develop ultralow-loss fiber glass.
Real-time x-ray diffraction to examine elastic–plastic deformation in shocked lithium fluoride crystals
Authors: Rigg P. A. , Gupta Y. M.
Published: July 2002

An experimental method was developed to obtain quantitative, x-ray diffraction data in laboratory plate impact experiments. This method was used to examine lattice compression accompanying elastic and elastic–plastic deformation in shocked LiF single crystals by imposing well-characterized, macroscopic uniaxial strain along the [111] and [100] axes, respectively. The [111] results reveal that the unit cell undergoes a one-dimensional compression; in contrast, the [100] results reveal an isotropic compression of the unit cell. The implications of the present results and the ability to make quantitative measurements are discussed.
Bright organic electroluminescent devices having a metal-doped electron-injecting layer
Authors: Kido Junji , Matsumoto Toshio
Published: July 2002

Bright organic electroluminescent devices were developed using a metal-doped organic layer as an electron-injecting layer at the interface between the cathode and the emitter layer. The typical device structure is a glass substrate/indium-tin oxide/arylamine/tris(8-quinolinolato)Al (Alq)/metal-doped Alq/Al. Dopant metals are highly reactive metals such as Li, Sr, and Sm. A device with Li-doped Alq layer showed high luminance of over 30 000 cd/m2, while a device without the metal-doped Alq layer exhibited only 3400 cd/m2. These results suggest that the Li doping to the Alq layer generates the radical anions of Alq serving as intrinsic electron carriers, which result in low barrier height for electron injection and high electron conductivity of the Li-doped Alq layer.
Can lead nonstoichiometry influence ferroelectric properties of Pb(Zr,Ti)O3 thin films?
Authors: Aggarwal S. , Madhukar S. , Nagaraj B. , Jenkins I. G. , Ramesh R. , Boyer L. , Evans J. T.
Published: July 2002

In this letter, we report on the influence of lead content on thin-film ferroelectric properties of lead niobium zirconate titanate. These films were prepared by the sol-gel technique and deposited on (La,Sr)CoO3 electrodes. It was determined that 7% excess lead in the sol was required to obtain nominally stoichiometric films. Lead deficiency in the film results in lead vacancies and excess lead is accommodated by forming octahedral site vacancies. Further amounts of lead in the sol leads to second phase PbO, which then coexists with the perovskite phase. The charged vacancies are compensated by mobile holes, which can interact with domains during switching. Under applied field and short pulse widths, the films with larger number of holes exhibited poor switching. Significant polarization relaxation was measured for films with excess lead, which is attributed to interaction of ionic defects with domains. Our results indicate that lead excess leads to poor reliability properties,whereas lead deficiency suppresses the polarization of the capacitors.
Phonon deformation potentials of α-GaN and -AlN: An ab initio calculation
Authors: Wagner J.-M. , Bechstedt F.
Published: July 2002

First-principles density functional theory calculations of the deformation potentials are presented for zone-center phonons in GaN and AlN in the wurtzite structure. Three cases of deformations are considered: biaxial and uniaxial strain along the c axis as well as hydrostatic compression. For the resulting atomic structures the phonon frequencies are determined. The combination of calculations for these deformations allows the derivation of elastic constants and phonon deformation potentials. Good agreement is observed with measured values for GaN. No published values for AlN are available.
Crystallization of bulk amorphous Zr–Ti(Nb)–Cu–Ni–Al
Authors: Löffler Jörg F. , Bossuyt Sven , Glade Stephen C. , Johnson William L. , Wagner Werner , Thiyagarajan P.
Published: July 2002

Small-angle neutron scattering (SANS) and transmission electron microscopy were used to resolve the crystallization of the bulk amorphous alloys Zr52.5Ti5Cu17.9Ni14.6Al10 (Vit105) and Zr57Nb5Cu15.4Ni12.6Al10 (Vit106). Decomposition and nanocrystallization were observed in both alloy compositions in the temperature regime from the glass transition, Tg, up to at least 90 K above Tg. From in situ SANS measurements on Vit105, chemical diffusion data were obtained whose temperature dependence follows an Arrhenius law. Normalizing the temperature to Tg, the diffusion data of Vit105 are very similar to those of the well-investigated bulk amorphous alloy Zr41.2Ti13.8Cu12.5Ni10Be22.5.
Hydrogen dynamics in [Me(H2O)6](ClO4)2 with Me=Mg, Mn, Fe, Ni, and Zn investigated with quasielastic neutron scattering
Authors: Nöldeke C. , Asmussen B. , Press W. , Büttner H. , Kearley G. , Lechner R. E. , Rufflé B.
Published: July 2002

The hydrogen dynamics in the metalhexahydrateperchlorates with Mg, Mn, Fe, Ni, and Zn as metal ions has been investigated with quasielastic neutron scattering. The water molecules perform 180°-flip motions on a picosecond time scale through a series of solid–solid phase transitions. In the highest temperature phase I and the subsequent phase II, rotational barriers of typically Ea=50 meV are found. These values are surprisingly small in view of the low symmetry of H2O molecules. The I → II phase transition has only very small effects on the hydrogen dynamics. At the transition into phase III an increase of the rotational barriers to typically Ea=250 meV is found. This is interpreted as the formation of weak hydrogen bonds. In phase I 180°-flip motions provide a complete description of the observed data. In phases II and III an extension of the dynamical model toward a stronger localization of hydrogen is required. A preference is given to a mechanism leading to a temporary blockade of the flip motions. In phase III of the Fe compound, the existence of crystallographically different sites for water molecules is inferred.
Multiple dynamical pathways in the O(1D)+CH4 reaction: A comprehensive crossed beam study
Authors: Lin J. J. , Shu J. , Lee Y. T. , Yang X.
Published: July 2002

In this report, the O(1D)+CH4 reaction has been reinvestigated using universal crossed molecular beam methods. Angular resolved time-of-flight spectra have been measured for various reaction channels of the title reaction: OH+CH3, H+H2COH/H3CO, and H2+HCOH/H2CO. Different product angular distributions have been observed for these product channels, indicating that these reaction channels occur via distinctive dynamical pathways. This study provides an excellent example of multiple dynamical pathways in a single chemical reaction, which opens enormous opportunities in investigating the dynamics of complicated chemical reactions that are important in combustion and atmospheric chemistry, and also provides a link between kinetics studies and dynamical research.
Josephson voltage standards
Authors: Hamilton Clark A.
Published: July 2002

This paper reviews the development and use of Josephson voltage standards over the last 30 years, including classical dc standards, programmable standards based on binary weighted arrays, pulse-driven delta–sigma standards for ac wave-form synthesis, and single-flux-quantum voltage multipliers.
Resistive modes in the edge and scrape-off layer of diverted tokamaks
Authors: Myra J. R. , D’Ippolito D. A. , Xu X. Q. , Cohen R. H.
Published: July 2002

The linear behavior of resistive ballooning modes in the edge and scrape-off layer of diverted tokamaks is explored in the context of a collisional fluid model. It is shown that the large magnetic shear and small poloidal field in the X-point region act to increase the wave number, and hence the importance of resistivity, near the X point. The resulting “disconnection” of the eigenmodes across the X point profoundly influences the unstable spectrum. A new class of modes called resistive X-point (RX) modes exploits this synergism between resistivity and the X-point geometry, giving rise to robust growth rates at moderate-to-low mode numbers. Relative to an equivalent limited plasma, the diverted plasma is shown to be more unstable in the edge (inside the separatrix), and more stable in the scrape-off layer.
Continuum state spectroscopy: A high resolution ion imaging study of IBr photolysis in the wavelength range 440–685 nm
Authors: Wrede Eckart , Laubach Stefan , Schulenburg Sonja , Brown Alex , Wouters Eloy R. , Orr-Ewing Andrew J. , Ashfold Michael N. R.
Published: July 2002

The photodissociation of jet-cooled IBr molecules has been investigated at numerous excitation wavelengths in the range 440–685 nm using a state-of-art ion imaging spectrometer operating under optimal conditions for velocity mapping. Image analysis provides precise threshold energies for the ground, I(2P3/2)+Br(2P3/2), and first excited [I(2P3/2)+Br(2P1/2)] dissociation asymptotes, the electronic branching into these two active product channels, and the recoil anisotropy of each set of products, as a function of excitation wavelength. Such experimental data have allowed mapping of the partial cross-sections for parallel (i.e., ΔΩ=0) and perpendicular (i.e., ΔΩ=±1) absorptions and thus deconvolution of the separately measured (room temperature) parent absorption spectrum into contributions associated with excitation to the A 3Π(1), B 3Π(0+) and 1Π(1) excited states of IBr. Such analyses of the continuous absorption spectrum of IBr, taken together with previous spectroscopic data for the bound levels supported by the A and B state potentials, has allowed determination of the potential energy curves for, and (R independent) transition moments to, each of these excited states. Further wave packet calculations, which reproduce, quantitatively, the experimentally measured wavelength dependent product channel branching ratios and product recoil anisotropies, serve to confirm the accuracy of the excited state potential energy functions so derived and define the value (120 cm−1) of the strength of the coupling between the bound (B) and dissociative (Y) diabatic states of 0+ symmetry.
Strong impact of x-ray radiation associated with electron beam metallization of diamond devices
Authors: Hordequin C. , Tromson D. , Brambilla A. , Bergonzo P. , Foulon F.
Published: July 2002

Electron-beam evaporation of metal contact is commonly used in the fabrication of semiconductor devices. We have observed that device irradiation by x-ray photons, which are generated by electrons striking the metal (titanium or gold) to be evaporated, has a strong impact on the characteristics of diamond devices used for radiation detection. It results in an improvement of the detector charge collection efficiency by a factor of 1.5 with respect to nonirradiated devices (standard thermal evaporation). Thermally stimulated current measurements showed that this effect is related to deep trap filling by free carriers generated in diamond by x-ray photons impinging the device during e-beam evaporation. Trap filling results in an increase of the free carrier drift distance before trapping. Study of contact annealing and the thermal stability of trap filling showed that charge detrapping at temperatures above 200 °C annihilates the observed detector sensitivity improvement.
Trap engineering in organic hole transport materials
Authors: von Malm N. , Steiger J. , Schmechel R. , von Seggern H.
Published: July 2002

Chemical impurities with known highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energies were incorporated in organic hole transport materials. The effect of these dopants on quantity and depth of trap levels, transport properties, and luminescence of organic light emitting devices was examined. This was achieved by investigating current–voltage characteristics, luminance–voltage characteristics, and utilizing the method of thermally stimulated current for trap level detection. It was found that 4,4′,4″-tris-[N-(1-naphthyl)-N-(phenylamino)]triphenylamine (1-NaphDATA) doped into N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine (α-NPD) generates a trap level whose activation energy corresponds to the HOMO energy difference between dopant and matrix molecules. Therefore, the detected electronic states can be assigned to hole traps. The influence of those traps on the charge transport will be reported. For doping α-NPD into 1-NaphDATA no new trap levels could be detected.
Silicoboron–carbonitride ceramics: A class of high-temperature, dopable electronic materials
Authors: Ramakrishnan P. A. , Wang Y. T. , Balzar D. , An Linan , Haluschka C. , Riedel R. , Hermann A. M.
Published: July 2002

The structure and electronic properties of polymer-derived silicoboron–carbonitride ceramics are reported. Structural analysis using radial-distribution-function formalism showed that the local structure is comprised of Si tetrahedra with B, C, and N at the corners. Boron doping of SiCN leads to enhanced p-type conductivity (0.1 Ω−1 cm−1 at room temperature). The conductivity variation with temperature for both SiCN and SiBCN ceramics shows Mott’s variable range hopping behavior in these materials, characteristic of a highly defective semiconductor. The SiBCN ceramic has a low, positive value of thermopower, which is probably due to a compensation mechanism.
Elastic solution for liquid-bridging-induced microscale contact
Authors: Fan H. , Gao Y. X.
Published: July 2002

Microscale contact between two solid surfaces induced by the liquid-bridging force is studied in the present article. Attention is focused on the interaction between the size of the contact area and the magnitude of the liquid-bridging force. The liquid-bridging force is related to the contact size and the other parameters, such as the filling angle, the contact angles, and the surface tension of the liquid, by solving the Laplace–Young equation. A singular integral equation for the coupled contact equilibrium problem is established and solved. Two approximate solutions for the same problem are also given and compared with the solution of the singular integral equation. Parametric study reveals the dependence of the semicontact width and the liquid-bridging force on the filling angle and the dimensionless group in the microscale contact.
Damping of relativistic electron beams by synchrotron radiation
Authors: Andersson F. , Helander P. , Eriksson L.-G.
Published: July 2002

Relativistic electrons emit synchrotron radiation due to their gyro- and guiding-center motions in a curved magnetic field. In this article, the kinetic theory of relativistic electron beams is developed to account for radiation reaction by including the Abraham–Lorentz reaction force in the kinetic equation. As an application of this theory, the dynamics of runaway electrons is examined and a steady-state solution is constructed describing a balance between acceleration by the electric field, pitch-angle scattering, and radiation reaction. Furthermore, it is found that a beam of relativistic electrons can be slowed down by the combined effects of pitch-angle scattering and radiation reaction. This damping can be more efficient than ordinary collisional drag, and appears to explain the decay of post-disruption runaway currents in the Joint European Torus (JET) [R. D. Gill, Nucl. Fusion 33, 1613 (1993)].
High energy ions and nuclear fusion in laser–cluster interaction
Authors: Kishimoto Y. , Masaki T. , Tajima T.
Published: July 2002

Highly efficient energy conversion of laser to high-energy components of ions and resulting rapid expansion take place upon the laser irradiation of clusters. Depending on the interrelationship between cluster size a and the electron excursion length ξe (which is related to the laser field amplitude), the expansion characteristics is categorized into the Coulomb explosion (a≪ξe) and alternative hydrodynamic ambipolar expansion (a≫ξe), revealing different features in the ion energy distribution. In the Coulomb explosion regime, a flat and/or slightly inverted ion energy distribution effective for enhanced fusion reactivity is generated. The critical cluster size and laser field amplitude which demarcate the expansion characteristics is investigated and the optimal fusion cross section is found in the domain of Coulomb explosion. A high fusion neutron yield is expected in the Coulomb explosion regime with greater cluster size and higher packing fraction.
The effects of mixing molecular gases on plasma parameters in a system with a grid-controlled electron temperature
Authors: Bai K. H. , Hong J. I. , You S. J. , Choi C. K. , Chang H. Y.
Published: July 2002

Plasma parameter variations as a function of a mixing ratio in an electron temperature control system using a grid are investigated. Under the grid, the electron temperature, as well as electron density, is a strong function of a mixing ratio. The electron temperature decreases with a mixing ratio of molecular gases (O2 and CF4), and the large inelastic cross section of molecular gas is the reason for the decrease in the electron temperature. When the length of sheath around the grid wires is comparable to the space between the grid wires, only 10% mixing of CF4 decreases the electron temperature to 0.8 eV in 10 mTorr Ar/CF4 plasma.