bluuebunny/crossref_metadata_2025 huggingface dataset:
Surgery for stress incontinence: factors associated with a successful outcome
Authors: Hutchings  , Griffiths  , Black
Published: July 2002

Objective

To investigate which patient and health‐service factors are predictive of outcome after surgery for stress incontinence.

Patients and methods

In all, 232 women were assessed before and 3, 6 and 12 months after surgery for stress incontinence. Twelve patient characteristics and seven health‐service factors were considered. Successful outcome was assessed in four ways: avoidance of complications after discharge, reduction in symptom severity, reduction in the social impact of stress incontinence, and improvement in activities of daily living (ADL). Relationships between possible predictors and outcome were explored using logistic regression models.

Results

Complications were less likely (r2=0.11) in women over 50 years of age, with no comorbidity and no urgency/urge incontinence, operated on by a gynaecologist. Reduction in symptom severity was more likely (r2=0.21) in younger women (≤50 years) with little limitation in their ADL, who suffered from severe or very severe stress incontinence symptoms but no urgency or urge incontinence, and who underwent preoperative urodynamic tests. A reduction in symptom impact was more likely (r2=0.15) in women in whom symptoms were having a moderate or severe impact, who were not grossly overweight, and who underwent a colposuspension or needle suspension performed by a gynaecologist. The only factor associated with improvement in ADL was the preoperative ADL score, i.e. the more limited a woman, the greater the likelihood of improvement (r2=0.15). The study provided evidence to support several of the widely held views about surgical success. Good outcomes were more likely if there is no urge incontinence, there is no or only mild comorbidity, no or only slight obesity, urodynamic investigations are conducted, and the surgeon is a gynaecologist. In contrast, there was no evidence that outcomes are worse if patients have undergone previous surgery for incontinence. Outcomes were also not related to grade of surgeon, surgeon’s workload, or teaching status of the hospital.

Conclusion

The relative importance of different factors depends on the outcome of interest, i.e. impairment (complications), disability (symptom severity) or handicap (symptom impact and ADL). These findings might help to improve clinical practice by indicating those characteristics that are associated with a greater likelihood of a good outcome. The results could also aid evaluation and audit of surgery, having identified the main prognostic factors that need to be considered when comparing the outcome of different procedures, surgeons or hospitals. Before doing so, the predictive models described in this paper need to be tested using an independent dataset.
Psychiatric and Neuropsychological Problems in Epilepsy Surgery: Analysis of 100 Cases That Underwent Surgery
Authors: Mayanagi Yoshiaki , Watanabe Eiju , Nagahori Yukihiro , Nankai Masahiro
Published: July 2002

Summary:  Purpose: For the past 20 years (1978–1997), a series of 100 cases of uncontrolled epilepsy had surgery in our department under the stated standard for surgical indications and were followed up for 2–22 years after surgery.

Methods: We evaluated 70 cases of temporal lobectomy, 20 cases of neocortical focal resection, and 10 cases of corpus callosotomy.

Results: Analysis of postoperative seizure control showed that 78 cases were class 1 or 2 (no or rare seizures), 14 cases were class 3 (worthwhile improvement), and eight cases were class 4 (no improvement). As generally accepted, temporal lobectomy was the most effective operative procedure, yielding excellent or good results in 87% of the 70 cases so treated. Among the nine cases in whom various psychiatric symptoms developed after surgery, four cases showed neurotic and five cases psychotic symptoms. Patients with psychosis had delusions of various types as a core symptom, combined with other symptoms such as anxiety, irritability, aggression, and depressive state. In two patients with psychosis who had episodes of delusions in the interictal phase before surgery, the symptoms were extremely resistant. The full IQ score of the Wechsler Adult Intelligence Scale–Revised (WAIS‐R) was increased after temporal lobectomy in 75% of the cases (p < 0.01; n = 44). The general MQ score in 31 cases, however, showed a 50:50 split between increase and decrease postoperatively. In correlation with the dominance of language by the Wada test, the general MQ score in the 15 cases of nondominant temporal lobe resection showed a significant increase (p < 0.05); whereas the MQ in the 16 cases of dominant‐side operation did not change.

Conclusions: Our new test, in which hippocampal stimulation and supraspan learning are combined, seems to be efficient for estimating the postoperative outcome of memory function.
Linker Histones and HMG1 Proteins of Higher Plants
Authors: Jerzmanowski A. , Przewłoka M. , Grasser K. D.
Published: July 2002

Abstract: Linker histones and the proteins belonging to the high mobility group 1 (HMG1) family are the most abundant proteins associated with the internucleosomal linker DNA in eukaryotic chromatin. Despite their relative abundance, there are indications that they may be involved in specific developmental pathways. In higher plants, a variety of these chromosomal proteins has been identified and characterized. In this report, we give an overview of the present knowledge about these two protein families, and discuss their likely functions in plants.
Resonant optical transmission and coupling in phase-locked diode laser arrays of antiguides: The resonant optical waveguide array
Authors: Botez D. , Mawst L. J. , Peterson G. , Roth T. J.
Published: July 2002

Uniform linear arrays of antiguides have 100% optical transmission between elements when the interelement spacing is an integer number of leaky wave half-wavelengths in the lateral direction. Resonant in-phase-mode and out-of-phase-mode coupling occurs when the number of half-wavelengths is odd and even, respectively. Such devices are called resonant optical waveguide (ROW) arrays. The discrimination between the resonant array mode and adjacent array modes reaches a maximum in close proximity to the resonance. An AlGaAs/GaAs ROW diode laser array operating close to resonance is demonstrated. Devices with virtually uniform near-field intensity profiles operate in stable, diffraction-limited in-phase modes to drive levels in excess of three times threshold.
Brillouin light scattering on chemical-vapor-deposited polycrystalline diamond: Evaluation of the elastic moduli
Authors: Jiang X. , Harzer J. V. , Hillebrands B. , Wild Ch. , Koidl P.
Published: July 2002

We report on Brillouin light scattering investigations on chemical-vapor-deposited polycrystalline diamond films. Besides the longitudinal and two transverse acoustic bulk phonons, a Rayleigh surface mode is observed. From the bulk modes the elastic constants c11, c12, and c44 of 1062±74, 122±8, and 541±22 GPa, respectively, are determined exhibiting the characteristic values of natural diamond. The observed Rayleigh mode sound velocity of 10326±470 m/s is consistent with the (110) texture of the polycrystalline film and the determined elastic constants.
Loss of optical nonlinearity in proton-exchanged LiNbO3 waveguides
Authors: Laurell F. , Roelofs M. G. , Hsiung H.
Published: July 2002

The second-order optical nonlinearity in a planar waveguide of proton-exchanged LiNbO3 is directly probed by second-harmonic generation from 532 to 266 nm in a reflection geometry. Compared to untreated LiNbO3, a 30-fold reduction in the optical nonlinearity is observed. Contrary to previous reports, we find that the optical nonlinearity cannot be effectively restored by thermal annealing.
Synthesis of CeC2 crystals encapsulated within gigantic super fullerenes
Authors: Yosida Yositaka
Published: July 2002

A new synthesis of nanometer-sized crystals encapsulated within gigantic super fullerenes by dc arc evaporation of composite carbon rods containing ∼3 wt % CeO2 is reported. Transmission electron microscopy showed the crystals CeC2 with the CaC2 type structure.
Effect of crystallographic orientation on ferroelectric properties of PbZr0.2Ti0.8O3 thin films
Authors: Ramesh R. , Sands T. , Keramidas V. G.
Published: July 2002

We report on the effect of cooling rate on the crystallographic orientation and ferroelectric properties of PbZr0.2Ti0.8O3 (PZT) thin films grown on a lattice matched bottom electrode such as c-axis oriented Y-Ba-Cu-O (YBCO). The cooling rate from deposition temperature influences the crystallographic orientation of the ferroelectric c axis of the PZT film as well as the electrical properties of the YBCO bottom electrode. As the volume fraction of the ferroelectric phase with the c axis in the plane of the film becomes higher, the hysteresis loops become more rounded and the polarization values become smaller. Highly c-axis oriented films, obtained by cooling from the growth temperature at 20 °C/min, show an almost square hysteresis loop with the largest polarization values.
Misfit dislocation nucleation in doped and undoped ZnSe/GaAs
Authors: Kuo L. H. , Salamanca-Riba L. , DePuydt J. M. , Cheng H. , Qiu J.
Published: July 2002

We have observed that undoped ZnSe films grown on GaAs substrates by molecular beam epitaxy show an irregular array of interfacial 60° misfit dislocations. However, N and Cl doping of the ZnSe thin films changes the interfacial dislocation structure. p-type ZnSe with N concentrations of ∼1018/cm3 shows a regular array of interfacial 60° misfit dislocations and a lower (∼1×106/cm2) density of threading dislocations compared to undoped films. However, samples with doping levels higher than 1019/cm3 show a density of threading dislocations of ∼108/cm2. These differences are explained in terms of Frank partial dislocations observed only in doped ZnSe. The Frank partial dislocations act as nucleation sites for the misfit dislocations. Thus, different mechanisms for the formation of misfit dislocations in doped and undoped films occur in this system.
Identification of phosphorus in diamond thin films using electron paramagnetic-resonance spectroscopy
Authors: Zvanut M. E. , Carlos W. E. , Freitas J. A. , Jamison K. D. , Hellmer R. P.
Published: July 2002

An electron paramagnetic-resonance study of diamond films doped by implantation of phosphorus during film deposition is reported. Samples with nominal phosphorus concentration between 1016 and 1017 cm−3 exhibit two isotropic lines of equal intensity separated by 27 G. The double-line spectrum is expected for a nuclear-spin 1/2 species such as phosphorus. The symmetry of the center and the temperature dependence of the spin concentration suggest that phosphorus forms a substitutional shallow donor in diamond.
Empirical formula for the dielectric constant of cubic semiconductors
Authors: Nag B. R.
Published: July 2002

Empirical formulae are presented relating the dielectric constants of cubic semiconductors with the average atomic number of the constituent atoms. The inverses of the constants are found to be linearly related to the average atomic number with a square foot mean percentage error of less than 0.25% for elemental semiconductors, 1.3% for gallium and indium compounds, 3.4% for aluminium compounds, 1.4% for II-VI compounds, and 1.2% for lead compounds. Usefulness of the formulae is also illustrated for identifying incorrect values and for estimating unknown values.
Apparatus for measuring photopolymerization exotherms
Authors: Pargellis A. N.
Published: July 2002

The resultant exotherms obtained from the photopolymerization of thin-film chemical samples have been investigated. The radiant source used is a standard 200-W in.−1 mercury discharge lamp. About 55% of this power is in the infrared (IR) part of the spectrum, which is removed by a water-cooled quartz tube. Different regions of the remaining spectrum were selected in the range 270–450 nm with cuton filters. A grating spectrometer is used to measure the transmitted spectra. A thin foil heat flow sensor is used as a calorimeter to measure the heat given off by a chemical sample when exposed to 0.5-s pulses of ultraviolet (UV) radiation. The pulse is formed by means of a bistable electronic shutter. Data were taken for samples ranging from 0.0125 to 0.05 mm [0.5 to 2.0 milli-inch (mils)] thicknesses. The heat output per gram is largest for the thinner samples and the absorption characteristics were observed to depend on the thickness of the sample.
Electron suppressors for negative ion sources
Authors: McAdams R. , King R. F. , Newman A. F.
Published: July 2002

Two designs of electron suppressor have been tested in a volume negative ion source operating dc with a large extraction aperture diameter (16 mm). Both suppressors employ magnetic fields to divert the electrons near the extraction aperture onto collector electrodes. However, while one suppressor uses a fixed field produced by permanent magnets, the other employs a variable field produced by a solenoidal coil. These suppressors allow low values (3–4:1) of extracted electron to ion currents to be obtained. The results are compared with a diffusion model and a hydrodynamic model of the transport of the electrons across the magnetic field. They show that the hydrodynamic model gives a good description of the suppression and transport of the electrons.
Realization and modeling of a pseudomorphic (GaAs1−xSbx–InyGa1−yAs)/GaAs bilayer-quantum well
Authors: Peter M. , Winkler K. , Maier M. , Herres N. , Wagner J. , Fekete D. , Bachem K. H. , Richards D.
Published: July 2002

We have realized a (GaAs1−xSbx-InyGa 1−yAs)/GaAs bilayer-quantum well (BQW), which consists of two adjacent pseudomorphic layers of GaAs1−xSbx and InyGa1−yAs sandwiched between GaAs barriers. Photoluminescence was observed at longer wavelengths than those found for corresponding InyGa1−yAs/GaAs and GaAs1−xSbx/GaAs single quantum wells (SQW), which indicates a type-II band alignment in the BQW. The longest 300 K emission wavelength achieved so far was 1.332 μm. For an accurate determination of the band offset between GaAs1−xSbx and GaAs, required for a theoretical modeling of the interband transition energies of these BQWs, a large set of GaAs1−xSbx /GaAs SQWs was prepared from which a type-II band alignment was deduced, with the valence band discontinuity ratio Qv found to depend on the Sb concentration x (Qv=1.76+1.34 x). With this parameter it was possible to calculate the expected interband transition energies in a BQW structure without any adjustable parameters. The calculations are in agreement with experimental data within a range of ±4%.
Precision spectroscopy using the Lamb dip in a pure ion plasma
Authors: Barnes P. N. , Hart G. W.
Published: July 2002

The use of the Lamb dip as a technique for precision spectroscopy in a non-neutral plasma is explored through computer modeling. Using singly ionized magnesium as the ion and under typical pure ion plasma conditions, the measurement appears to be feasible. Under the conditions calculated here, the Lamb dip is only 4% wider than the natural linewidth of the transition.
High energy scattering beamlines at European Synchrotron Radiation Facility
Authors: Suortti P. , Tschentscher Th.
Published: July 2002

The scientific background and scope of research at the High Energy Scattering Beamlines of the European Synchrotron Radiation Facility are reviewed briefly. The beamline has two different insertion devices (IDs), a permanent magnet multipole wiggler and a superconducting wavelength shifter. The IDs can be used alternatingly, and both provide circularly polarized radiation off the orbit plane up to energies of several hundreds of keV. Measurements of the spectral brightness and the polarization components by energy dispersive powder diffraction and Compton scattering from iron in an alternating magnetic field are presented and compared with calculations based on source parameters. The beamline optics are based on use of horizontally reflecting bent Si crystals. These provide various focusing geometries, and the calculated flux of monochromatic radiation is given at energies between 30 and 175 keV. The maximum of 2×1012 photons/s is reached at 80 keV. The main experimental apparatus in the initial operation includes a high-resolution three-axis diffractometer, and a scanning-type Compton spectrometer.
Comparison of numerical and experimental simulation of a beryllium window under intense heat load
Authors: Gambitta A. , Zanini F. , Poloni C. , Visintin A.
Published: July 2002

Synchrotron radiation emitted by insertion devices provides a much higher power density than that from conventional bending magnets. In this case thermal stress induced by absorbed radiation produces intense mechanical deformations which can break beryllium windows in very short times. Numerical and experimental results show that nonlinear analysis in the plastic region of beryllium is needed to predict failure of windows under intense heat load.
The Australian National Beamline Facility at the Photon Factory (abstract)
Authors: Garrett R. F. , Cookson D. J. , Foran G. , Creagh D. C. , Wilkins S. W.
Published: July 2002

The Australian National Beamline Facility has been installed at the Photon Factory, Tsukuba, Japan. The construction and operation of the facility has been funded by a consortium of Australian research organizations, universities, and government funding agencies, with the aim of providing Australian scientists with routine access to synchrotron radiation in the hard-x-ray region. The first experiments were performed at the ANBF in November 1992. The facility consists of a general purpose x-ray-beamline, including a simple two-crystal monochromator, delivering either monochromatic x rays (range 5–20 keV) or white radiation to the experimental hutch. The main experimental instrument, a multiconfiguration diffractometer, has recently been installed at the beamline. This unique instrument combines vacuum operation and imaging plate detectors, and can be configured for high-resolution powder diffraction (including a time resolved mode), protein crystallography, and triple-axis experiments. In addition, the white or monochromatic beam can pass through the diffractometer to a secondary experimental table, where experiments such as EXAFS, Laue diffraction, topography, and microbeam measurements are performed. Details of the beamline, monochromator, and diffractometer optics and performance will be described, and an overview will be given of the experimental capabilities of the facility.
Design and operation of a UHV double-bounce harmonic rejection mirror for XAFS studies
Authors: Lamble G. M.
Published: July 2002

A simple but effective harmonic rejection system has been installed on beamline X-11B at the NSLS. The system includes a parallel pair of nickel-coated float glass mirrors. This geometry allows an output beam whose direction is independent of the incidence angle on the mirrors. They are housed within a UHV chamber and situated 2.0 m upstream of the sample position and 8 m downstream of a double crystal monochromator. The angle of the mirror pair is adjusted by a single stepper motor. In its current configuration the double-bounce system works for energies between about 2 and 6 keV. For harmonic rejection of energies higher than this, the whole device may be repositioned to permit a single bounce of the x-ray beam from one of the mirrors. The features and operation of this simple device are discussed.
Low temperature diffractometer below 1 K by a 3He-4He dilution refrigerator used for synchrotron radiation x-ray diffraction
Authors: Nakajima Tetsuo , Ohta Joji , Yonenaga Ichiro , Koizumi Hirokazu , Iwasa Izumi , Suzuki Haruhiko , Suzuki Takayoshi , Suzuki Hideji
Published: July 2002

The observation of changes in the crystal structure at low temperatures plays very important roles in gaining a better understanding of mechanism of the phase transformation and stability of the phase as a ground state. For these purposes, two sets of 3He-4He dilution refrigerators with a top loading facility were installed at BL-3C2 and 6C1 of the Photon Factory. The former is used exclusively for taking topographs from quantum crystals of solid 3He and 4He for studies of lattice defects. Typical examples of topographs, which indicate an annealing effect of solid helium which might be understood from a viewpoint of a quantum tunneling effect, are presented. The latter refrigerator is used for studies of crystalline solids by x-ray diffraction. A splitting of the Laue spots of Cs2NaHoCl6 below 150 mK, giving evidence of a Jahn–Teller transition of the first kind, which is the lowest transition temperature ever detected, was observed as a new peculiarity of the phase transition at ultralow temperature.
Simulation of scattering x rays for improving image quality in SR coronary angiography
Authors: Oku Y. , Aizawa K. , Hyodo K. , Ando M.
Published: July 2002

Coronary angiography by intravenous injection of contrast material using synchrotron radiation (SR) is a safe and easy method for diagnosis of coronary arteries. In Japan, a two-dimensional imaging system for coronary angiography is being developed. In that case, there exists a problem: Image contrast and visibility deteriorate due to harmful scattering x rays which are made when passing through a patient’s body. Therefore, we have developed a simulation program in order to study the x-ray scattering behavior in a subject using monochromatic x rays and to find a method to decrease the scattering x rays in images using x-ray grids. The calculated results concerning the scattering x rays using the simulation program were compared with experimental results using monochromatic x rays at 33.17 keV from synchrotron radiation.
Micromachining with a force microscope tip assisted by electrostatic force
Authors: Goto Kazuya , Hane Kazuhiro
Published: July 2002

We present a new technique for surface modification with a force microscope tip. By using electrostatic force between a cantilever and a sample surface, deformation on the surface can be performed with a very large load on the order of 10−6 N, even if the spring constant of the cantilever is small (on the order of 10−2 N/m). Because the tip does not shift laterally while the load is applied, pits are produced with precise positioning. Furthermore, very fast response of the modification on the order of 10−6 s was obtained.
A low temperature focused ion beam system: Application to in situ processing of high T
c superconducting devices
Authors: Assayag G. Ben , Gierack J. , Flament S. , Dolabdjian C. , Gire F. , Lesquey E. , Gunther C. , Hamet J. F. , Prouteau C. , Robbes D.
Published: July 2002

A modified focused ion beam (FIB) equipment is described. It enables real time imaging by electron scanning microscopy during the FIB milling of cooled samples down to 82 K with liquid N2 cooling, or down to 25 K with liquid He cooling. Experimental results on the patterning of high Tc YBaCuO superconducting thin films are given which show the possibility of ‘‘in situ’’ control of the critical current of micro or nanosuperconducting bridges during the milling. The application of this FIB system to the design of a microthermometer, operating in the pẆ/√Hz range, and of a SQUID, whose Josephson effects correspond to a coherent vortex flow in nanobridges, is detailed.
A bond graph model for the sample extraction/injection system of a microsized gas chromatographic instrument
Authors: Lin Jie , Wang Wanjun , Murphy Michael C. , Overton Edward
Published: July 2002

A bond graph model of the sample extraction/injection system of a prototype portable gas chromatographic instrument has been developed. In addition to performing the same functions as current portable gas chromatographs (GCs), the new generation of GC instruments is designed to perform extraction of analytes from liquid and solid samples. The prototype instrument achieves these improvements by taking of advantage of microfabrication technologies and microprocessor control in the design. A novel sample extraction/injection module is essential to the improved performance of the portable instrument, which will include microfabricated components such as inlets, interface chips, fluid channels, control valves, optimal heater/sensor combinations, and multiport connectors. In order to achieve the desired analytical performance, all of the major components are heated to 250 °C during different stages of a sample analysis. Predicting the performance of the system in this operating regime requires the modeling and analysis of system behavior in two interacting energy domains, fluid and thermal. This article represents the first effort to understand the dynamic behavior of the thermofluid aspect of micro-GC instruments and one of the first attempts to apply the widely-used bond graph technique to modeling and analysis of microsized thermofluid systems. Simulation results using the bond graph model closely match available experimental data, with differences typically less than 10%. This demonstrates that fluid dynamic theory for macroscale systems, and the bond graph method based on it, can be readily applied to microscale systems with these dimensions. The bond graph method can be a useful computer-aided design tool for the development of a new generation of truly integrated micro-GC instruments and sensors fabricated with micromachining technology.
Performance of a high-resolution, synchrotron-based, small-angle x-ray scattering instrument
Authors: Wilcoxon J. P. , Craft S. A. , Thurston T. R.
Published: July 2002

We describe the construction and performance of a small-angle x-ray scattering (SAXS) instrument which we have used on several beam lines at the National Synchrotron Light Source. The analyzer crystal was a channel cut Si(1,1,1) designed for use at λ=1.54 Å with a measured efficiency of 60% and an angular resolution full width at half maximum of 0.001°. In the case of strongly scattering samples (i.e., powders), momentum transfer q between 1×10−4 Å<q<0.1 Å−1 could be studied with over eight decades of dynamic intensity range. We demonstrate the versatility of this instrument by performing scattering experiments on a variety of spherical latex samples spanning the size range from 50 to 800 nm, liquid crystal samples with sharp, asymmetrical Bragg peaks, and metal clusters with sizes less than 10 nm. Small-angle x-ray scattering data for the larger polystyrene samples is compared with light scattering data and theoretical structure factors, and the relative roles of instrument smearing, sample polydispersity, and interparticle interference are elucidated. In the case of the liquid crystal samples, the high resolution of the instrument allows structural features to be observed that were previously obscured by the instrumental resolution in other small-angle neutron and synchroton-based Kratky camera data taken on the same samples.
High-resolution scanning microdensitometer
Authors: Feldman Martin , Chunsheng Zhang
Published: July 2002

A technique has been developed to enhance the resolution of an optical scanning microdensitometer. Phase shifting optics are used to obtain a signal with high resolution, but with a complex structure. This signal is subtracted from a reference signal to produce the equivalent of an isolated, very narrow, bright line. This line is then scanned across the specimen. Improvements in resolution of about a factor of 2, compared to a conventional optical system, have been observed at numerical apertures up to 0.55, without sacrificing either the working distance or the depth of focus.
Valved molecular beam skimmer
Authors: Marceca Ernesto , Becker Jörg A. , Hensel Friedrich
Published: July 2002

Under routine source conditions, the optimum nozzle-skimmer distance to achieve maximum molecular beam intensities is within the range of a few millimeters. In cases where double skimming is additionally required, the distance between the skimmers should be kept small in order to sample a sufficiently large solid angle of the beam and hence maintain a good enough intensity. These two facts make it normally difficult to isolate the first from the second expansion chamber using a commercial vacuum gate valve due to the lack of remaining space. This note presents the design of a vacuum-tight valve which allows the aperture of a skimmer to be closed by plugging a needle directly against its internal conical wall. The valve can be driven manually or pneumatically from outside the vacuum chamber. The helium conductance of the valve was measured to be better than 1×10−8 mbar×l×s−1 for a helium partial pressure difference of 1 bar.
An automated spring balance for kinetic gravimetric sorption of gases and vapors in polymers
Authors: McDowell C. C. , Coker D. T. , Freeman B. D.
Published: July 2002

A method for automation of a McBain-type spring balance using a charge coupled device camera, a computer equipped with a frame-grabber card, and National Institutes of Health Image software is presented. This balance is used to study the sorption and transport of small molecules in polymeric materials. Kinetic gravimetric sorption data of acetone uptake in a random copolymer of 50 wt % poly(ethylene terephthalate) and 50 wt % poly(ethylene 2,6-naphthalate) at 35 °C are provided to illustrate the utility of the method. The diffusion coefficients determined from the cathetometer and camera experiments are 1.1±0.2×10−12 and 1.0±0.2×10−12 cm2/s, respectively. At an acetone partial pressure of 5.4 cm Hg, the equilibrium acetone uptake was 1.47±0.15 g acetone/100 g polymer using the cathetometer to determine spring extension and 1.52±0.15 g acetone/100 g polymer when the camera was used to determine mass uptake of acetone by the polymer. The camera-based balance was determined to be sensitive to weight changes as small as ±1 μg.
Status report on ECR ion source operation at the GSI accelerator facilities
Authors: Tinschert K. , Bossler J. , Schennach S. , Schulte H.
Published: July 2002

The Caprice electron cyclotron resonance (ECR) ion source of the high charge state injector (HLI) as standard injection line for the UNILAC at GSI is now in permanent operation during all beam time periods of a year. So the ECR test stand which is equipped with the same version of Caprice mainly has to be used for preparatory work. Ion beams of a great variety of elements are demanded covering beam time periods of up to six weeks. Besides the stable and reliable operation with diverse gases the application of our high-temperature oven has become a standard method for all solid materials attaining a vapor pressure of 10−3 mbar between 800 and 1500 °C. It has been operated not only with pure metal samples but also with especially produced isotopic zinc oxide samples providing a stable beam of Zn10+68 ions. Alternatively a low-temperature evaporator was constructed for high vapor pressure materials and was used for the production of Se and Zn ions. Experiences gained with the oven and evaporator method will be reported and results will be summarized. In order to investigate and improve ion extraction and beam transport through the low energy beam line under conditions equivalent to the HLI a new ECR injector setup is being built which is equipped with an identical analyzing system. The basic concept of the new setup is described.
An improved extraction for the multicusp-type light ion-ion source apparatus
Authors: Reijonen J. , Heikkinen P. , Liukkonen E. , Ärje J.
Published: July 2002

A new ion extraction system has been developed for use with the light ion source apparatus (LIISA) of the Accelerator Laboratory. The aim of the new extraction system is to have a more intense and better quality beam. For simulation of the beam behavior at the extraction region a computer code IGUNe has been used. The simulation shows that a simple triode extraction would be efficient enough to extract total beam intensities of around 5 mA at an extraction voltage of 10–15 kV. At the same time, with the carefully designed plasma electrode, the emittance could be decreased significantly from the original design. The new extraction was installed in May 1997 and the results have been encouraging. The transport efficiency of the extracted beam to the first Faraday cup (at a distance of 1.2 m) was 100% and the maximum proton current obtained was 2.0 mA. The maximum proton current in the cyclotron inflector is 1.0 mA, which is eight times larger than the previous record.
Imaging of optical inhomogeneities in highly diffusive media: Discrimination between scattering and absorption contributions
Authors: Cubeddu R. , Pifferi A. , Taroni P. , Torricelli A. , Valentini G.
Published: July 2002

An effective projection imaging technique is proposed that allows not only detection of realistic optical inhomogeneities in highly diffusive media, but also the discrimination between scattering and absorption contributions. The method is based on information derived from time-resolved transmittance measurements. Scattering inhomogeneities are discriminated using maps of the transport scattering coefficient, as provided by best fitting of the diffusion theory to experimental data. Absorption variations are effectively classified by time gating on the tail of the transmittance pulse.
X-ray spectroscopic studies of hot, dense iron plasma formed by subpicosecond high intensity KrF laser irradiation
Authors: Nazir K. , Rose S. J. , Djaoui A. , Tallents G. J. , Holden M. G. , Norreys P. A. , Fews P. , Zhang J. , Failles F.
Published: July 2002

The time-integrated x-ray emission from a hot, dense iron plasma has been recorded. The iron plasma was created when a target with a 1000-Å-thick iron layer buried beneath 1000 Å of plastic was irradiated by a 300 fs pulse of 249 nm laser light at an intensity of approximately 1017 W cm−2. Two models have been used to construct a synthetic x-ray spectrum. The first employs detailed, spectroscopically accurate atomic data and the second uses a local thermodynamic equilibrium opacity model. The detailed model shows fairly good agreement with experiment whereas the opacity model only shows agreement in the gross features.
Substrate dependence on the optical properties of Al2O3 films grown by atomic layer deposition
Authors: Kim Y. , Lee S. M. , Park C. S. , Lee S. I. , Lee M. Y.
Published: July 2002

The atomic layer deposition technique has been applied to the growth of Al2O3 thin films on the substrates of Si(100), 100-nm-thick SiO2 covered Si(100) [SiO2/Si(100)], and 90-nm-thick TiN covered SiO2/Si(100). The growth rate of Al2O3 films was 0.19 nm/cycle and identical for all substrates employed under the surface controlled process. However, the optical properties of Al2O3 films were significantly affected by different substrates. The average interband-oscillator energy and refractive index parameter were determined to be 3.330 eV and 2.992×10−14 eV m2 for Al2O3 film grown on Si(100), while those for the film grown on SiO2/Si(100) were 4.492 eV and 2.074×10−14 eV m2, respectively.
The intrinsic temperature effect of the Raman spectra of graphite
Authors: Tan PingHeng , Deng YuanMing , Zhao Qian , Cheng WenChao
Published: July 2002

The Raman spectra of ion-implanted highly oriented pyrolytic graphite (HOPG) are reported, in which an additional mode at 1083 cm−1 and three doublet structures in the positions of ∼1350, ∼2450, and ∼2710 cm−1 are revealed. Noticeable frequency shifts are observed for all the Raman bands between the spectra excited with different laser powers, which are interpreted as the pure temperature effect and a downshift in the C–C stretching frequency induced by the thermal expansion. Moreover, the pure temperature effect (dω/dT)V without anharmonic contribution is achieved in pristine HOPG. The results suggest that the pure temperature effect without anharmonic contribution plays an important role in the frequency shifts with temperature.
The effect of Si doping on the defect structure of GaN/AlN/Si(111)
Authors: Molina S. I. , Sánchez A. M. , Pacheco F. J. , Garcı́a R. , Sánchez-Garcı́a M. A. , Sánchez F. J. , Calleja E.
Published: July 2002

The effect of Si doping on the structural quality of wurtzite GaN layers grown by molecular beam epitaxy on AlN buffered (111) Si substrates is studied. The planar defect density in the grown GaN layer strongly increases with Si doping. The dislocation density at the free surface of GaN significantly decreases when Si doping overpasses a limit value. Si doping affects the misorientation of the subgrains that constitutes the mosaic structure of GaN. The increase of the planar defect density and out-plane misorientation angles of the GaN subgrains with Si doping explain the decrease of dislocations that reach the free surface of GaN. A redshift in the photoluminescence spectra together with a decrease in the c-axis lattice parameter as the Si doping increases point to an increase in the residual biaxial tensile strain in the GaN samples.
Electro-optic sampling near zero optical transmission point
Authors: Jiang Zhiping , Sun F. G. , Chen Q. , Zhang X.-C.
Published: July 2002

Theoretical calculation and experimental demonstration indicate that there is an optimal position near the zero optical bias point in a crossed polarizer electro-optic sampling geometry. At this position, free-space electro-optic sampling with a ZnTe sensor crystal has the largest modulation depth for the detection of a weak (THz) modulated signal on a strong laser background. Electro-optic sampling of THz pulses with a modulation depth of 9% and a signal-to-noise ratio better than 50 000:1 is demonstrated.
Direct measurement of minority carriers diffusion length using Kelvin probe force microscopy
Authors: Meoded T. , Shikler R. , Fried N. , Rosenwaks Y.
Published: July 2002

We report on the use of Kelvin force microscopy as a method for measuring very short minority carrier diffusion length in semiconductors. The method is based on measuring the surface photovoltage between the tip of an atomic force microscope and the surface of an illuminated semiconductor junction. The photogenerated carriers diffuse to the junction, and change the contact potential difference between the tip and the sample as a function of the distance from the junction edge. The diffusion length L is then obtained by fitting the measured contact potential difference using the minority carrier continuity equation. The method is applied to measurements of electron diffusion lengths in GaP epilayers.
Slow passage through a transcritical bifurcation for Hamiltonian systems and the change in action due to a nonhyperbolic homoclinic orbit
Authors: Haberman Richard
Published: July 2002

One-degree of freedom conservative slowly varying Hamiltonian systems are analyzed in the case in which a saddle-center pair undergo a transcritical bifurcation. We analyze the case in which the method of averaging predicts the solution crosses the unperturbed homoclinic orbit at the precise time at which the transcritical bifurcation occurs. For the slow passage through the nonhyperbolic homoclinic orbit associated with a transcritical bifurcation, the solution consists of a large sequence of nonhyperbolic homoclinic orbits surrounded by autonomous nonlinear saddle approaches. The change in action is computed by matching these solutions to those obtained by averaging, valid before and after crossing the nonhyperbolic homoclinic orbit. For initial conditions near the stable manifold of the nonhyperbolic saddle point, one saddle approach has particularly small energy and instead satisfies a nonautonomous nonlinear equation, which provides a transition between nonhyperbolic homoclinic orbits, centers, and saddles.
Plasma cleaning and nitridation of sapphire (α-Al2O3) surfaces: New evidence from in situ real time ellipsometry
Authors: Losurdo M. , Capezzuto P. , Bruno G.
Published: July 2002

The interaction of α-Al2O3 (0001) surfaces with H atoms and N atoms from remote rf plasmas used for the cleaning and nitridation processes, respectively, is investigated at temperatures in the range of 200–600 °C. The chemistry and kinetics of the above processes are monitored in real time by in situ spectroscopic ellipsometry. Also, the chemistry of the nitrided sapphire surfaces is verified by x-ray photoelectron spectroscopy (XPS) analysis. Specifically, H atoms treatments are effective in removing carbon contaminants from the sapphire surface at temperatures of 200–400 °C. Real time ellipsometry is suitable to detect the cleaning end point and to verify the onset of the H-atom diffusion into the sapphire substrate. Remote N2 plasma nitridation at 200 °C is found to yield homogeneous and smooth AlN layers of about 5 Å, after approximately 25 min of nitridation, whereas high nitridation temperatures result in a damaged sapphire surface with AlN protrusions. Both ellipsometric and XPS data show that the sapphire nitridation can be interpreted in the framework of a chemical model, where the formation of NO competes with AlN formation. The chemisorption equilibrium of NO, which strongly depends on surface temperature, is the key factor controlling the nitridation chemistry and kinetics.
Statistical analysis of the low-temperature α peak of the internal friction in iron single crystals
Authors: Natsik V. D. , Pal-Val P. P. , Pal-Val L. N. , Semerenko Yu. A.
Published: July 2002

The effect of changes in the ultrasonic frequency or in the dislocation structure of the samples on the parameters of the low-temperature α peak of the internal friction and the Young’s modulus defect corresponding to it is investigated experimentally in single crystals of pure iron. A statistical interpretation of the temperature dependence and structural sensitivity of the characteristics of the dynamic relaxation in the neighborhood of the α peak is proposed, based on the assumption of a random scatter of the values of the activation energy of the elementary relaxators. Empirical estimates are obtained for the attempt period and for the mean value and variance of the activation energy of the relaxation process responsible for the α peak of the internal friction in iron.
Semiclassical molecular dynamics simulations of intramolecular proton transfer in photoexcited 2-(2′-hydroxyphenyl)–oxazole
Authors: Guallar Victor , Batista Victor S. , Miller William H.
Published: July 2002

A full-dimensional excited state potential energy surface is constructed, and the proton transfer dynamics associated with the keto-enolic tautomerization reaction in photoexcited 2-(2′-hydroxyphenyl)–oxazole is simulated according to an approximate version of the semiclassical initial value representation method introduced by Miller and co-workers [V. Guallar, V. S. Batista, and W. H. Miller, J. Chem. Phys. 110, 9922 (1999)]. The full-dimensional potential energy surface is developed according to an ab initio reaction surface model obtained at the CIS level of quantum chemistry. Proton transfer is found to be substantially affected by isotopic substitution, and significantly coupled to the internal oxazole–hydroxyphenyl in-the-plane bending mode. The nascent tautomer is found to be stabilized primarily through vibrational energy redistribution into all of the remaining in-the-plane vibrational modes. The accuracy of the methodology is verified by reducing the dimensionality of the system and comparing our semiclassical results with full quantum mechanical calculations.
Raman microprobe polarization measurements as a tool for studying the structure and orientation of molecules and clusters incorporated into cubic zeolites: S8 and Se12 rings in zeolite A
Authors: Poborchii Vladimir V.
Published: July 2002

Raman spectra of molecules or clusters incorporated into cubic zeolites are usually studied using microcrystalline powder samples, light being completely unpolarized because of multiple reflection on microcrystal surfaces. Therefore, all information about symmetry of the Raman-active vibrations of species and orientation of species in zeolite cavities is lost. In order to save this information, we propose to do Raman microprobe polarization measurements of cubic zeolite single crystals containing examined species. We theoretically consider examples of high-symmetry anisotropic species (planelike or rodlike molecules or clusters with the threefold or higher major axes) incorporated into cubic zeolite A. We experimentally study polarization and angular dependencies of Raman spectra of S8 and Se12 rings incorporated into zeolite A single crystal. The obtained dependencies correspond to the C4v point group symmetry S8 rings oriented by their fourfold axes along the fourfold axes of zeolite and the D3d point group symmetry Se12 rings oriented by their threefold axes along the threefold axes of zeolite. The method applied to the S8 and Se12 rings is considered as a new powerful tool for studying the structure and orientation of a wide class of cubic-zeolite-confined species.
A semiclassical limit for the mapping Hamiltonian approach to electronically nonadiabatic dynamics
Authors: Bonella S. , Coker D. F.
Published: July 2002

In this paper we derive a semiclassical limit of dynamics corresponding to the mapping Hamiltonian formulation of the electronically nonadiabatic problem originally proposed by Stock and co-workers, and Miller and his group. We show results comparing the approach described here with the alternative semiclassical scheme previously used by these workers in applications of this formulation. For simplicity the calculations presented here are for single potential surface models but the approach is generally applicable to many coupled surfaces. We demonstrate by comparison with exact numerical solution that the results obtained with the approach presented here are accurate for arbitrary potential forms but that the alternative semiclassical implementation only apparently converges when repulsive walls in the model surfaces are unimportant.
Optical mode loss and gain of multiple-layer quantum-dot lasers
Authors: Smowton P. M. , Herrmann E. , Ning Y. , Summers H. D. , Blood P. , Hopkinson M.
Published: July 2002

Using an electrically pumped multisection technique, we have directly measured the internal optical mode loss of semiconductor-laser structures containing 1, 3, 5, and 7 layers of uncoupled InGaAs quantum dots. The optical loss does not increase with the number of dot layers so higher net modal gain can be achieved by using multiple layers. The maximum modal gain obtained from the ground state increases with dot layer number from 10±4 cm−1 for a single layer to 49±4 cm−1 for the 7 layer sample, which is typical of the threshold gain requirement of a 350 μm long device with uncoated facets.
Charge dynamics in silicon nitride/silicon oxide double layers
Authors: Zhang Xiaoqing , Sessler Gerhard M.
Published: July 2002

Transport of positive charge deposited by a corona discharge on the open nitride surface of a silicon nitride (150 nm)/silicon oxide (300 nm) double layer on silicon substrate is studied by determining the location of the charge centroid with a capacitance–voltage method used in conjunction with surface-potential measurements. At temperatures of about 400 °C, the charge is mobile in the nitride and a large part of it is eventually trapped at the nitride/oxide interface while some of the charge reaches the substrate through the oxide. Indications are that at this temperature the mean free path of positive charges in the nitride and oxide layers is comparable to the layer thicknesses, but much shorter in the nitride at lower temperatures.
Strain-driven self-positioning of micromachined structures
Authors: Vaccaro Pablo O. , Kubota Kazuyoshi , Aida Tahito
Published: July 2002

We introduce a method to make self-positioned micromachined structures by using the strain in a pair of lattice-mismatched epitaxial layers. This method allows the fabrication of simple and robust hinges for movable parts, and it can be applied to any pair of lattice-mismatched epitaxial layers, in semiconductors or metals. As an application example, a standing mirror was fabricated. A multilayer structure including an AlGaAs/GaAs dielectric mirror and an InGaAs strained layer was grown by molecular-beam epitaxy on a GaAs substrate. After releasing the multilayer structure from the substrate by selective etching, it moved to its final position powered by the strain release in the InGaAs layer.