bluuebunny/crossref_metadata_2025 huggingface dataset:
Master scaling of perceived intensity of touch, cold and warmth
Authors: Berglund Birgitta , Harju Eva‐Liz
Published: June 2003

A new approach is presented for scaling perceived intensity of touch, cold and warmth based on magnitude estimation. In this method named master scaling thenar is utilized as common reference area for scaling and calibrating perceived intensity. The master scaling is particularly well suited for clinical applications in which the stimulation in pain‐affected body areas creates a complex perception (e.g., paradoxical heat for cold stimulation) and/or aberrant psychophysical functions for perceived intensity. The results from three different experiments showed that: (a) All patients and healthy subjects were able to scale adequately the perceived intensity of touch, cold, and warmth at unaffected body areas. (b) Thenar stimulations were shown to be adequate common references in the joint scaling of perceived intensity of other body areas in pain patients as well as healthy persons. (c) Individual thenar psychophysical functions can be used for screening patients and healthy persons with regard to their ability to scale perceived intensity of touch, cold and warmth. (d) Master scaled perceived intensity scales can be used for determining if various pain‐unaffected body areas are normal or abnormal in patients and in healthy persons. (e) The interindividual variation in perceived intensity is considerably reduced after master scaling and approaches that of intraindividual variation as found in olfaction and hearing. Finally, empirically based thenar Master Functions of perceived intensity for touch, cold and warmth are proposed to be used in future sensory testing of patients, as well as of healthy persons.
Spinal cord injury pain
Authors: Beric Aleksandar
Published: June 2003

Awareness that SCI pain is common emerged during the past decade. However, there are a number of unresolved issues. There is a need for variety of experimental models to reflect diversity of SCI pains. Current classification is not as user‐friendly as it should be. More attention should be given to a condition of the spinal cord below and above the SCI lesion. A consensus for what is an optimal SCI functional assessment for patients with sensory complaints and pain should be developed. Further extensive SCI pain research is needed prior to spinal cord regeneration trials in order to be able to cope with a potential for newly developed pains that may appear during incomplete spinal cord regenerative attempts.
How Ulf Lindblom changed my life: studies of the mechanisms of pain and abnormal sensations following nerve injury and their treatment in cats, rats and humans
Authors: Wiesenfeld‐Hallin Zsuzsanna
Published: June 2003

This is a personal account of the long term scientific relationship with Professor Ulf Lindblom.
Cardiac troponin I in cats with hypertrophic cardiomyopathy
Authors: Connolly DJ , Cannata J , Boswood A , Archer J , Groves E.A , Neiger R
Published: June 2003

The molecular structure of cardiac troponin I (cTnI) is highly conserved across mammalian species and assays developed for its measurement in human patients have been validated in a number of veterinary species. A raised concentration of circulating cTnI is a sensitive and specific marker of cardiac myocyte injury. Raised levels have been documented in a variety of cardiac diseases in both human and veterinary patients. This study compared serum cTnI concentrations between 16 cats diagnosed with hypertrophic cardiomyopathy (HCM) using echocardiography and 18 control cats. The results show that cats with HCM have significantly higher concentration of serum cTnI (median 0.95 ng/ml, range 0.2–4.1 ng/ml) than control cats (median <0.2 ng/ml, range <0.2–0.25 ng/ml) [ P<0.0001]. Furthermore in cats with cardiomyopathy a weak correlation was found between the thickness of the left ventricular freewall in diastole measured by ultrasound and serum cTnI concentration (r2=0.28; P=0.036). These results suggest that measurement of serum cTnI concentration may enable cats with cardiomyopathy to be distinguished from normal cats using the assay described here.
Spatial distribution of phytoplankton along the Sunda Islands: The monsoon anomaly in 1998
Authors: Asanuma Ichio , Matsumoto Kazuhiko , Okano Hirofumi , Kawano Takeshi , Hendiarti Nani , Sachoemar Suhendar I.
Published: June 2003

Recent ocean color and microwave observations are used to assess the spatial distribution of phytoplankton blooming relative to monsoons along the Sunda Islands. In 1997 and 1999, during the northwest monsoon the eastward South Java Current (SJC) along the Sunda Islands restrained the flows from the straits along the Sunda Islands and ceased blooming. During the southeast monsoon the westward South Equatorial Current (SEC) and the southeasterly wind generated cyclonic eddies along the Sunda Islands. The blooming was observed over those cyclonic eddies, where nutrients were entrained to the surface. In 1998, through the northwest to the southeast monsoon the eastward currents were flowing away from the coast. During the southeast monsoon the SEC was not observed. Through 1998, cyclonic eddies were observed along the Sunda Islands in consequence of these anomalies. The distribution of currents is defined for the monsoon anomaly in 1998. (1) The eastward SJC flowed away from the coast in the northwest monsoon. (2) No westward SEC was observed in the southeast monsoon. (3) The eastward SJC restrained the flow from the straits in the southeast monsoon. (4) Chlorophyll a ∼1 mg m−3 were observed along the Sunda Islands through the year. This monsoon anomaly is hypothesized as a result of anomalies in the distribution of pressure systems between the Pacific and the Indian Ocean following to the El Niño.
Record heavy Asian dust in Beijing in 2002: Observations and model analysis of recent events
Authors: Sugimoto Nobuo , Uno Itsushi , Nishikawa Masataka , Shimizu Atsushi , Matsui Ichiro , Dong Xuhui , Chen Yan , Quan Hao
Published: June 2003

A record heavy Yellow Sand event was observed on 20 March in Beijing. This event was unusual because the wind speed was low and the dust concentration was extremely high at the dust front. Observations with a polarization lidar, an optical particle counter, and a high‐volume sampler were performed throughout the event in Beijing. The visibility derived from the lidar data was 650 m, and the total suspended particle concentration was 11 mg/m3 at the peak. Chemical transport model analysis revealed that the main part of the dust originated in the Mongolian border area near Ejinaqi. This dust event severely affected Korea and northern Japan. Continuous lidar observations in Beijing, Nagasaki and Tsukuba revealed that the frequency of dust events in 2001 and 2002 was similar in Beijing but much higher in 2002 in Nagasaki and Tsukuba. The model showed dust was transported to the east more frequently in 2002 and the difference is probably related to the smaller perturbation of the westerly jet. This indicates that a slight change in climate can cause a large difference in dust phenomena in the northwestern Pacific region.
Observations of large aerosol infrared forcing at the surface
Authors: Vogelmann Andrew M. , Flatau Piotr J. , Szczodrak Malgorzata , Markowicz Krzysztof M. , Minnett Peter J.
Published: June 2003

Studies of aerosol effects on the Earth’s energy budget usually consider only the cooling effects at short (solar) wavelengths, but we demonstrate that they also have important warming effects at thermal infrared (IR) wavelengths that have rarely been observed and are commonly ignored in climate models. We use high‐resolution spectra to obtain the IR radiative forcing at the surface for aerosols encountered in the outflow from northeastern Asia. The spectra were measured by the Marine‐Atmospheric Emitted Radiance Interferometer (M‐AERI) from the NOAA Ship Ronald H. Brown during the Aerosol Characterization Experiment‐Asia (ACE‐Asia). We show that the daytime surface IR forcing are often a few Wm−2 and can reach almost 10 Wm−2 for large aerosol loadings. Thus, even the smaller aerosol IR forcing observed here are comparable to or greater than the 1 to 2 Wm−2 IR surface enhancement from increases in greenhouse gases. These results highlight the importance of aerosol IR forcing which should be included in climate model simulations.
Observations of discrete, global magnetospheric oscillations directly driven by solar wind density variations
Authors: Kepko L. , Spence H. E.
Published: June 2003

In this paper we present six events in which both the time series and the spectral content of solar wind number density fluctuations and magnetospheric magnetic field observations were highly correlated for intervals ranging from a few to twelve hours. The fluctuations were periodic and occurred at discrete frequencies which often matched the f = 1.3, 1.9, 2.6, and 3.4 mHz oscillations that have been attributed to global magnetospheric MHD cavity and/or waveguide modes. We also observed significant power in the sub‐mHz region, with frequencies as low as f = 0.1 mHz. We show that these fluctuations were first observed in the solar wind, far upstream from the Earth, and argue that the convected density perturbations slowly alter the size of the magnetospheric cavity leading to the appearance of multiple, discrete magnetospheric oscillations. We argue that for these events the discrete frequencies were an inherent property of the solar wind and were not related to a possible cavity or waveguide mode of the magnetosphere. We then show that the density fluctuations, when converted into length scales, organize into scale sizes of L = 23, 30, 45, and 80–100 RE. Finally, we speculate on a possible solar source for the periodic solar wind structures.
Spatial and temporal variations in biogenic volatile organic compound emissions for Africa south of the equator
Authors: Otter L. , Guenther A. , Wiedinmyer C. , Fleming G. , Harley P. , Greenberg J.
Published: June 2003

Improved vegetation distribution and emission data for Africa south of the equator were developed for the Southern African Regional Science Initiative (SAFARI 2000) and were combined with biogenic volatile organic compound (BVOC) emission measurements to estimate BVOC emissions for the southern African region. The BVOCs are estimated to total 80 Tg C yr−1 for the region, with isoprene and monoterpenes contributing 56 and 7 Tg C yr−1, respectively. The large uncertainties, particularly in terms of basal emission capacity assignment, associated with these outputs are discussed. Woodlands are predicted to be the dominant vegetation type, covering 23% of southern Africa, and are the largest annual source of isoprene (20 Tg C), monoterpenes (3 Tg C), and other VOCs (4 Tg C). Mopane savannas and woodlands are predicted to contribute over 75% of all monoterpenes, primarily from light‐dependent emission processes. Rain forests cover only 3.5% of the total area but have high annual emission rates (9.8 g C m−2 yr−1). In the tropical regions with high rainfall, warm temperatures, and high plant productivity throughout the year, the seasonal variation in VOC emissions was small. In subtropical regions, dominated by highly seasonal savannas and grasslands, large variations were predicted, with emissions declining by up to 85% during dry winter periods (June–August) due to low leaf area index after leaf drop.
High‐resolution elemental records from the South China Sea and their paleoproductivity implications
Authors: Wei Gangjian , Liu Ying , Li Xianhua , Chen Muhong , Wei Wuchang
Published: June 2003

The biogenic‐related elements Ca, Sr, Ba, P, Cd, scavenged Al, and Ti were analyzed by inductively coupled plasma mass spectrometry (ICP‐MS) and inductively coupled plasma atomic emission spectrometry (ICP‐AES) for Core NS93‐5 from the west slope of the South China Sea. Terrestrial input as estimated from the accumulation of Ti was higher during glacials than during interglacials. Carbonate accumulation rates are inversely related to those of terrestrial input, suggesting higher production of calcareous phytoplankton during interglacials. The accumulation patterns of authigenic Sr, Ba, P, and Cd match that of carbonate, further indicating higher calcareous phytoplankton production during interglacials. Scavenged Al and excess SiO2, which is related to biogenic opal, exhibit higher accumulation rates during glacials and correspond with changes in terrestrial input. This indicates that terrestrial input driven is important to siliceous phytoplankton production but not for calcareous phytoplankton production. As calcareous phytoplankton is the dominant component of the biogenic sediments in the South China Sea, particularly during interglacials, previous inference of higher productivity in the South China Sea during glacials based on only the biogenic opal proxy needs to be reconsidered.
Skill in real‐time solar wind shock forecasts
Authors: Mozer J. B. , Briggs W. M.
Published: June 2003

Forecasts of 96 shocks in the solar wind at the L1 point made by the HAF kinematic solar wind model made between 5 February and 31 December 2001 are compared with algorithmically determined shocks from real‐time data from the SWEPAM and MAG instruments aboard the ACE spacecraft. Traditional measures of forecast skill used by the meteorological community are applied to these forecasts and observations and indicate modest skill in the HAF model. Details of forecast skill are determined using the Briggs‐Ruppert skill score which incorporates the costs of forecast error. This new metric is shown by the present example to be a potentially valuable tool to the customer of space weather forecasts in that it focuses on the actual application of the forecasts and identifies economic regimes where a given forecast is potentially valuable.
On the orbital forcing of Martian water and CO2 cycles: A general circulation model study with simplified volatile schemes
Authors: Mischna Michael A. , Richardson Mark I. , Wilson R. John , McCleese Daniel J.
Published: June 2003

Variations in the Martian water and CO2 cycles with changes in orbital and rotational parameters are examined using the Geophysical Fluid Dynamics Laboratory Mars General Circulation Model. The model allows for arbitrary specification of obliquity, eccentricity, and argument of perihelion as well as the position and thickness of surface ice. Exchange of CO2 between the surface and atmosphere is modeled, generating seasonal cycles of surface ice and surface pressure. Water is allowed to exchange between the surface and atmosphere, cloud formation is treated, and both cloud and vapor are transported by modeled winds and diffusion. Exchange of water and CO2 with the subsurface is not allowed, and radiative effects of water vapor and clouds are not treated. The seasonal cycle of CO2 is found to become more extreme at high obliquity, as suggested by simple heat balance models. Maximum pressures remain largely the same, but the minima decrease substantially as more CO2 condenses in the more extensive polar night. Vapor and cloud abundances increase dramatically with obliquity. The stable location for surface ice moves equatorward with increasing obliquity, such that by 45° obliquity, water ice is stable in the tropics only. Ice is not spatially uniform, but rather found preferentially in regions of high thermal inertia or high topography. Eccentricity and argument of perihelion can provide a second‐order modification to the distribution of surface ice by altering the temporal distribution of insolation at the poles. Further model simulations reveal the robustness of these distributions for a variety of initial conditions. Our findings shed light on the nature of near‐surface, ice‐rich deposits at midlatitudes and low‐latitudes on Mars.
Space-Optimized Tree: A Connection+Enclosure Approach for the Visualization of Large Hierarchies
Authors: Nguyen Quang Vinh , Huang Mao Lin
Published: June 2003

This paper describes a new approach, space-optimized tree, for the visualization and navigation of tree-structured relational data. This technique can be used especially for the display of very large hierarchies in a two-dimensional space. We discuss the advantages and limitations of current techniques of tree visualization. Our strategy is to optimize the drawing of trees in a geometrical plane and maximize the utilization of display space by allowing more nodes and links to be displayed at a limited screen resolution. Space-optimized tree is a connection+ enclosure visualization approach that recursively positions children of a subtree into polygon areas and still uses a node–link diagram to present the entire hierarchical structure. To be able to handle the navigation of large hierarchies, we use a new hybrid viewing technique that combines two viewing methods, the modified semantic zooming and a focus+ context technique. While the semantic zooming technique can enlarge a particular viewing area by filtering out the rest of tree structure from the visualization, the focus+context technique allows the user to interactively focus, view and browse the entire visual structure with a reasonable high-density display.
Effect of confinement on DNA dynamics in microfluidic devices
Authors: Jendrejack Richard M. , Schwartz David C. , Graham Michael D. , de Pablo Juan J.
Published: June 2003

The dynamics of dissolved long-chain macromolecules are different in highly confined environments than in bulk solution. A computational method is presented here for detailed prediction of these dynamics, and applied to the behavior of ∼1–100 μm DNA in micron-scale channels. The method is comprised of a self-consistent coarse-grained Langevin description of the polymer dynamics and a numerical solution of the flow generated by the motion of polymer segments. Diffusivity and longest relaxation time show a broad crossover from free-solution to confined behavior centered about the point H≈10Sb, where H is the channel width and Sb is the free-solution chain radius of gyration. In large channels, the diffusivity is similar to that of a sphere diffusing along the centerline of a pore. For highly confined chains (H/Sb≪1), Rouse-type molecular weight scaling is observed for both translational diffusivity and longest relaxation time. In the highly confined region, the scaling of equilibrium length and relaxation time with H/Sb are in good agreement with scaling theories. In agreement with the results of Harden and Doi [J. Phys. Chem. 96, 4046 (1992)], we find that the diffusivity of highly confined chains does not follow the scaling relation predicted by Brochard and de Gennes [J. Chem. Phys. 67, 52 (1977)]; that relationship does not account for the interaction between chain and wall.
Response of an extraordinary magnetoresistance read head to a magnetic bit
Authors: Moussa J. , Ram-Mohan L. R. , Rowe A. C. H. , Solin S. A.
Published: June 2003

It has been proposed earlier that the extraordinary magnetoresistance (EMR) observed at room temperature in nonmagnetic semiconducting materials containing metallic inhomogeneities can be used in suitably constructed read heads for magnetic storage devices. Here, we show that such read heads are much simpler in design, and allow for higher sensitivity than is observed using magnetic layered structures that employ the phenomenon of giant magnetoresistance. We calculate, with no adjustable material parameters, the room-temperature response of an EMR read-head design, using finite element analysis, as a function of the position of the magnetic bit relative to the read head. The scaling property of the EMR bodes well for increasing the storage density to 1 Tbit/in.2 in the near future.
Numerical simulations of pattern-directed phase decomposition in a stressed, binary thin film
Authors: Wise S. M. , Johnson William C.
Published: June 2003

Two-dimensional simulations of the microstructural evolution of stressed, epitaxial, binary thin films on a geometrically patterned substrate using a Cahn–Hilliard equation are presented. Substrate and film are differentiated using a phase field parameter and both epitaxial and compositional strains for a cubic system under plane strain are treated. Numerical simulations show that arrays of nanoparticles can self-assemble in the decomposing film, especially near the film–substrate interface. The size and distribution of the precipitates in the film are sensitive to the geometry of the substrate interface, compositional and epitaxial strains, the film composition and thickness, and the interfacial interaction of the film with the substrate and with the surface. The simulations show the possibility of creating particle spacings considerably smaller than the substrate pattern periodicity, allowing a “demagnification” beyond the resolution of the imposed pattern.
Photoluminescence study of ZnO films prepared by thermal oxidation of Zn metallic films in air
Authors: Wang Y. G. , Lau S. P. , Lee H. W. , Yu S. F. , Tay B. K. , Zhang X. H. , Hng H. H.
Published: June 2003

Zinc oxide (ZnO) films were synthesized by thermal oxidation of metallic zinc films in air. The influence of annealing temperatures ranging from 320 to 1000 °C on the structural and optical properties of ZnO films is investigated systematically using x-ray diffraction and room temperature photoluminescence (PL). The films show a polycrystalline hexagonal wurtzite structure without preferred orientation. Room temperature PL spectra of the ZnO films display two emission bands, predominant excitonic ultraviolet (UV) emission and weak deep level visible emission. It is observed that the ZnO film annealed at 410 °C exhibits the strongest UV emission intensity and narrowest full width at half maximum (81 meV) among the temperature ranges studied. The excellent UV emission from the film annealed at 410 °C is attributed to the good crystalline quality of the ZnO film and the low rate of formation of intrinsic defects at such low temperature. The visible emission consists of two components in the green and yellow range, and they show different temperature dependent behavior from UV emission. Their possible origins are discussed.
Whole-cell heater for the diamond anvil cell
Authors: Dubrovinskaia Natalia , Dubrovinsky Leonid
Published: June 2003

An external heating assemblage allowing diamond anvil cell (DAC) experiments at megabar pressures and temperatures above 1200 K was constructed. The complete high-pressure high-temperature system consists of an anvil assembly made from a special high-temperature alloy, a mechanical loading mechanism, and external resistive heaters placed around the cell. The new system allows fine adjustment of the pressure (within 1 GPa) over the whole temperature range. It maintains constant pressure (within 1 GPa at megabar pressures) and constant temperature (within 5 K at 1000 K) for several hours. Temperature is measured with an external thermocouple. The pressure chamber does not have a measurable temperature gradient. The new heating assemblage is easily coupled with a experimental setup at synchrotron radiation facilities and Raman spectrometers. We tested the performance of the new system by measuring the thermal expansion of Fe0.90Ni0.05 at different pressures and by studying phase transformations in TiO2 and the melting curve of H2O.
Operational mechanism of light-emitting devices based on Ru(II) complexes: Evidence for electrochemical junction formation
Authors: Rudmann Hartmut , Shimada Satoru , Rubner Michael F.
Published: June 2003

In this work, the operational mechanism of single-layer light-emitting electrochemical cells (LECs) based on the small molecule tris(2,2’ bipyridyl) ruthenium(II) [Ru(II)] was investigated using capacitance and resistance measurements. The current–voltage and capacitance–voltage characteristics of such devices suggest that an electrochemical junction is formed during operation with a high electric field across the junction. A similar mechanism has been proposed for polymer LECs. In the case of Ru(II) devices, electrically conducting regions adjacent to the electrodes are the result of mixed-valent states that form due to oxidation and reduction of the complex. The junction thickness is a function of the type of counterions used and the operating voltage. Thinner junctions were observed for devices with high ionic conductivity and at higher operating voltages. Transient capacitance and resistance measurements show that the junction formation is faster in devices with higher ion mobility and during higher operating voltages. In addition, the capacitance and resistance exhibit a relaxation time after the device is turned off. This relaxation shows that the electrochemical junction stays present in a device for some time (several seconds to minutes) once a device is turned off. The electrochemical junction disappears as the counterions relax back. Furthermore, a theoretical model is presented, which shows that due to the concentration gradient of mixed-valent states during operation, an electric field has to be present in the device. The model also shows that there can be no local charge neutrality in the bulk of the device during operation.
Molecular collective dynamics in solid para-hydrogen and ortho-deuterium: The Parrinello–Rahman-type path integral centroid molecular dynamics approach
Authors: Saito Hiroaki , Nagao Hidemi , Nishikawa Kiyoshi , Kinugawa Kenichi
Published: June 2003

The single-particle and collective dynamics of hydrogen/deuterium molecules in solid hcp para-hydrogen (p-H2) and ortho-deuterium (o-D2) has been investigated by using the path integral centroid molecular dynamics (CMD) simulations at zero-pressure and 5.4 and 5.0 K, respectively. For this purpose, we have newly unified the standard CMD method with the Parrinello–Rahman–Nosé–Hoover-chain-type isothermal–isobaric technique. The phonon density of states have been obtained and the dynamic structure factors have been calculated to observe the phonon dispersion relations of both crystals. For solid p-H2, the high energy edge of the phonon energies of solid p-H2 is >13 meV, and the calculated phonon energies are significantly higher than those observed in Nielsen’s previous neutron scattering experiments in the energy region >9 meV. The relationship between the present results and the data reported so far is discussed to resolve the outstanding controversy regarding the phonon energies in solid p-H2. On the other hand, the excitation energies for solid o-D2 are in fairly good agreement with those of the neutron experiments. The calculated isothermal compressibility of solid p-H2 is found to be very close to the experimental result.
Thermal decomposition behavior of the HfO2/SiO2/Si system
Authors: Sayan S. , Garfunkel E. , Nishimura T. , Schulte W. H. , Gustafsson T. , Wilk G. D.
Published: June 2003

We report on the thermal decomposition of uncapped, ultrathin HfO2 films grown by chemical vapor deposition on SiO2/Si(100) substrates. Medium energy ion scattering, x-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy were used to examine the films after they had been annealed in vacuum to 900–1050 °C. Film decomposition is a strong function of the HfO2 overlayer thickness at a given temperature, but the underlying SiO2 layer thickness does not significantly affect the thermal stability of the HfO2 film. Oxygen diffusion in the system was monitored by O16/18O isotopic labeling methods. Direct evidence of silicide formation is observed upon decomposition.
Production of electronically excited CH via the vacuum ultraviolet photodissociation of ethylene and the possible role of the ethylidene isomer
Authors: O’Reilly John , Douin Stéphane , Boyé Séverine , Shafizadeh Niloufar , Gauyacq Dolores
Published: June 2003

The visible fluorescence of CH fragments (A 2Δ→X 2Π and B 2Σ−→X 2Π transitions) formed in the vacuum ultraviolet photodissociation of ethylene in the 11.7–21.4 eV energy region, was recorded. Two formation thresholds for each excited fragment, CH* (A) or CH* (B), were identified and associated with two dissociation channels namely CH*+CH3 and CH*+CH+H2. Unlike previous studies of the dissociation dynamics on the ground-state potential energy surface, neither of these channels exhibit an energy barrier within the experimental uncertainty, even in the latter case of molecular H2 elimination. It is proposed that both channels pass via an ethylidene intermediate (H3CCH:), an isomer never previously experimentally detected and whose existence has been debated in theoretical publications. The observed behavior, at the excitation energies used in the present work, also suggests that fast isomerization and internal conversion to excited states of ethylene precede fragmentation. Above 18.5 eV, that is around the ionization limit C2H4+ (D 2B1u), dissociative ionization starts to compete with neutral dissociation into excited CH fragments giving rise to a substantial decrease in the neutral fragment signal.
Hydrogen plasma treatment effects on electrical and optical properties of n-ZnO
Authors: Polyakov A. Y. , Smirnov N. B. , Govorkov A. V. , Ip K. , Overberg M. E. , Heo Y. W. , Norton D. P. , Pearton S. J. , Luo B. , Ren F. , Zavada J. M.
Published: June 2003

The effects of hydrogen plasma treatment on high-quality bulk n-ZnO crystals were studied. It is shown that after plasma exposure at 200 °C for 0.5 h the hydrogen penetrates into the material down to about 20 μm and shows concentrations close to 1017 cm−3 in that region. The incorporation of this hydrogen coincides with an increase in the shallow donor concentration to about the same level as the concentration of hydrogen. In contrast to that in most other semiconductor materials, hydrogen plasma treatment of ZnO is shown to increase the concentration of the already existing electron and hole traps and to introduce electron traps near 0.55 eV, earlier observed in proton irradiated samples. The effect is at least partially due to the surface damage caused by plasma exposure. Despite this increase in the density of deep traps, the luminescence intensity in the near band-edge region is shown to increase down to the depth corresponding to the hydrogen penetration depth in the material.
Role of oxygen pressure in growth of CeAlOx thin films on Si by pulsed laser deposition
Authors: Yan L. , Kong L. B. , Pan J. S. , Ong C. K.
Published: June 2003

( CeO y ) 0.67 ( Al 2 O 3 ) 0.33  (1.5⩽y⩽2) (CeAlOx) thin films were deposited on p-type Si (100) substrates by the pulsed laser deposition method at 650 °C. The effect of oxygen pressure on structural and thus dielectric properties of the CeAlOx films was extensively investigated. The CeAlOx thin films turned from a mixture of crystalline CeO2, Ce2O3, and Al2O3 to the amorphous CeAlO3 as the deposition oxygen pressure was decreased from 3.2×10−2 to 4.5×10−6 mbar. With decreasing oxygen pressure, Ce4+ content decreased while Ce3+ content increased. The reduction of Ce4+ to Ce3+ compensated the oxygen deficit as a result of the decreased oxygen pressure. The flatband voltage (VFB) of the CeAlOx thin films decreased with oxygen pressure due to the decreased fixed charges in the films. The increased leakage current density of films as a result of the reduction in oxygen pressure was probably attributed to the electron hopping conduction between Ce4+ and Ce3+ at middle pressure and poor leakage property of Ce2O3 at low pressure, respectively.
Electronic structure analysis of Zr silicate and Hf silicate films by using spatially resolved valence electron energy-loss spectroscopy
Authors: Ikarashi Nobuyuki , Manabe Kenzo
Published: June 2003

Electronic structures near the band gaps of Zr silicate and Hf silicate thin films were investigated experimentally and theoretically. We show that the electronic structure of Zr silicate can be reproduced by a superposition of the electronic structures of ZrO2 and SiO2. Similarly, the electronic structure of Hf silicate can be reproduced by a superposition of the electronic structures of HfO2 and SiO2. This indicates that, in these silicates, the lowest conduction band states are composed mostly of d states of Zr or Hf, and the valence band states mostly of O 2p states. The similarity of the electronic structures of these silicates can be attributed to the similarity of the chemical natures of Zr and Hf atoms. Consequently, when these silicate films are used as gate dielectrics in metal–oxide–semiconductor transistors, the gate leakage current could be strongly affected by d states of Zr or Hf.
Dielectric and transverse piezoelectric properties of sol-gel-derived (001) Pb[Yb1/2Nb1/2]O3–PbTiO3 epitaxial thin films
Authors: Zhou Q. F. , Zhang Q. Q. , Yoshimura T. , Trolier-McKinstry S.
Published: June 2003

(1−x) Pb [ Yb 1/2 Nb 1/2 ] O 3 –x PbTiO 3 (PYbN–PT, x=0.5) epitaxial thin films were deposited on (001) SrRuO3/(001) MgO substrates by sol-gel processing. X-ray diffraction analysis revealed that the films were pyrochlore-free (001) epitaxial films when crystallized at 750 °C for 1 min. The dielectric permittivity and loss factor varied only slightly with frequency in the range of 100 to 10 000 Hz. At 1 kHz, the dielectric permittivity was 870 and the dielectric loss was 0.03 at room temperature. Compared with (111) PYbN–PT films, (001) PYbN–PT films exhibited better ferroelectric and piezoelectric properties. The remanent polarization (Pr) was 37 μC/cm2. The effective transverse piezoelectric e31,f coefficient of the films were −10.2 C/m2 when films were poled at room temperature. Enhanced piezoelectric properties were obtained using unique two-step method poling the PYbN–PT films at higher temperatures.
Integrating sphere charge coupled device-based measurement method for organic light-emitting devices
Authors: Hong Yongtaek , Kanicki Jerzy
Published: June 2003

An integrating sphere charge coupled device (CCD)-based measurement system has been developed to accurately characterize the optoelectronic performance of organic polymer light-emitting devices (PLEDs). By theoretically analyzing a previously developed lens-coupled method and comparing it with the integrating sphere CCD-based method, we have found that the integrating sphere-based measurement method provides more stable reliable optical data in comparison with the lens-coupled measurement method. In addition, we demonstrate that inappropriate calibration of the PLED measurement system can greatly exaggerate device performance.
Time domain technique to measure solar cell capacitance
Authors: Kumar R. Anil , Suresh M. S. , Nagaraju J.
Published: June 2003

The solar cell capacitance is one of the important parameters for design of a reliable and efficient switching charge controller. In this article a time domain technique is used to measure the solar cell capacitance (charge equivalent). The measurements carried out on GaAs/Ge and BSFR silicon solar cells at different cell voltages are presented and compared with the charge equivalent capacitance derived from the impedance spectroscopy technique. It is observed that the time domain technique is simple, reliable, and can be used for on-line measurements of different types of solar cell/panel capacitance.
Effects of natural and electrochemical oxidation processes on acoustic waves in porous silicon films
Authors: Fan H. J. , Kuok M. H. , Ng S. C. , Lim H. S. , Liu N. N. , Boukherroub R. , Lockwood D. J.
Published: June 2003

Brillouin scattering has been performed to study the effects of natural and electrochemical oxidation on the surface and bulk acoustic mode properties of porous silicon films. The acoustic mode frequencies are observed to decrease with increasing oxidation time and this is attributed to the progressive transformation of silicon–silicon bonds on the inner pore walls into SiO2. The dependence of the surface and bulk acoustic mode frequencies on the natural oxidation time allows the evaluation of these wave frequencies for a porous-SiO2 glass film, and hence the estimation of its bulk modulus. Both Brillouin and Raman data confirm the expectation that oxidation leads to a reduction in silicon nanoparticle size, and provide a correlation between the redsifted acoustic mode frequency and the oxidation period.
Primary and secondary pyroelectric effects of ferroelectric 0-3 composites
Authors: Chew K.-H. , Shin F. G. , Ploss B. , Chan H. L. W. , Choy C. L.
Published: June 2003

Simple and tractable analytical expressions for determining the pyroelectricity in ferroelectric 0-3 composites have been developed. For the dilute suspension limit, expressions for the effective pyroelectric and other thermal electromechanical properties are derived within the framework of the Maxwell–Wagner approach. Then, an effective-medium theory is employed to examine the first and second pyroelectric coefficients in the concentrated suspension regime. The effective-medium approach as compared to the Maxwell–Wagner approach results in a better agreement with known experimental data up to higher volume fraction of inclusions. The pyroelectricity of 0-3 composites of ceramic inclusions embedded in the P(VDF–TrFE) copolymer matrix and of P(VDF–TrFE) inclusions embedded in a ceramic matrix are analyzed numerically under different polarization configurations. The theoretical predictions show that the secondary pyroelectric effects in composite systems with ceramic as the matrix are stronger than those with the copolymer as the matrix and can sometimes dominate the pyroelectricity for certain compositions.
Technique for measuring the groove density of diffraction gratings using the long trace profiler
Authors: Cocco D. , Sostero G. , Zangrando M.
Published: June 2003

Diffraction gratings are the most efficient systems for dispersing radiation in the soft x-ray and extreme ultraviolet region. They can have a constant periodic structure or a variable line spacing. The performance of an instrument adopting optics depends on the grating manufacturing errors. These could be both slope errors (routinely measured by various instruments) and undesired groove density variation. The measurement of the groove density is mainly performed with home-made setups, which use the diffraction pattern generated by a laser or, sometimes, the images collected with an atomic force microscope or a scanning tunneling microscope. With the use of a long trace profiler (LTP), an instrument developed to measure the longitudinal profile of a mirror, a method to measure the groove density (and the groove density variation) of a surface diffraction grating was developed. It consists of the measurement of the angle of a particular diffraction order, taking advantage of the extreme angular precision of the LTP. An accuracy of one part per million, or better, in the determination of the groove density constancy/variation, is reached. This method demonstrates the great versatility of the LTP and, in particular, its infinite depth of field.
Use of a double-paddle oscillator for the study of metallic films at high temperatures
Authors: Rösner P. , Samwer K. , Pohl R. O. , Schneider S.
Published: June 2003

We demonstrate the use of silicon double-paddle oscillators for the study of mechanical properties of thin films in the temperature range of 300–673 K under ultrahigh vacuum conditions. It is shown that even at these temperatures the damping coefficient Q−1 of one particular eigenmode of the bare paddle is lower than 10−5 and is explained through thermoelastic damping. This small background damping provides a sufficient sensitivity for investigations of mechanical properties of thin films above room temperature. As an application, shear modulus and internal friction are presented for a glassy metallic Zr65Al7.5Cu27.5 film of 300 nm thickness, deposited by simultaneous electron-beam evaporation of the pure elements. Glass transition and crystallization are observed.
Proton-exchanged waveguides in MgO-doped LiNbO3: Optical and structural properties
Authors: Korkishko Yu. N. , Fedorov V. A. , Kostritskii S. M. , Maslennikov E. I. , Frolova M. V. , Alkaev A. N. , Sada C. , Argiolas N. , Bazzan M.
Published: June 2003

We show that MgO:HxLi1−xNbO3 single crystalline solid solutions prepared by proton exchange exhibit very complex structural chemistry which is different from that for undoped congruent material. A correlation between the crystal structure and the refractive index profiles has been experimentally determined that allows us to explain specific peculiarities of the optical properties observed, as well as to predict the characteristics of a variety of waveguides. We have established that the well-known annealing proton exchange process leads to crystal structure disorder in MgO:LiNbO3 within the surface region of waveguides fabricated this way, but the soft proton exchange process preserves the crystal structure of magnesium-doped material.
Brillouin scattering study of ZnO
Authors: Azuhata T. , Takesada M. , Yagi T. , Shikanai A. , Chichibu SF. , Torii K. , Nakamura A. , Sota T. , Cantwell G. , Eason D. B. , Litton C. W.
Published: June 2003

Polarized Brillouin scattering measurements were carried out for a bulk ZnO single crystal. The whole set of elastic stiffness constants was determined to be c11=19.0, c12=11.0, c13=9.0, c33=19.6, c44=3.9, and c66=4.0 in units of 1011 dyn/cm2. The relationships between photoelastic constants at wavelength of 514.5 nm were also obtained: p11, p13, p44, and p66=1.8, 2.3, 0.50, and 0.38, respectively, relative to p12.
Photonic crystal laser sources for chemical detection
Authors: Lončar Marko , Scherer Axel , Qiu Yueming
Published: June 2003

We have realized photonic crystal lasers that permit the introduction of analyte within the peak of the optical field of the lasing mode. We have explored the design compromises for developing such sensitive low-threshold spectroscopy sources, and demonstrate the operation of photonic crystal lasers in different ambient organic solutions. We show that nanocavity lasers can be used to perform spectroscopic tests on femtoliter volumes of analyte, and propose to use these lasers for high-resolution spectroscopy with single-molecule sensitivity.
Limitations on the scale of an electrode array for trapping particles in microfluidics by positive dielectrophoresis
Authors: Markarian Nikolai , Yeksel Mike , Khusid Boris , Farmer Kenneth , Acrivos Andreas
Published: June 2003

Experiments were performed on dilute suspensions of polarized particles in microfluidics with electrodes of different sizes arranged parallel and perpendicular to the flow. We identified the conditions under which the interparticle electric interactions do not affect the particle trapping in the high-field strength regions. In particular, there exists a lower bound on the scale of the microelectrodes, below which the expected improvement in positioning the particles in the preselected locations cannot be attained.
The role of free carriers and excitons on the lasing characteristics of InAs/InGaAs quantum-dot lasers
Authors: Dikshit A. , Pikal J. M.
Published: June 2003

Temperature-dependent lasing characteristics of InAs/InGaAs quantum-dot lasers operating at 1.3 μm are theoretically analyzed. In particular, we investigated the effect of different carrier distribution models, free and bound electron–hole pairs, on gain and the lasing characteristics. In contrast to lasers of higher dimensionality, the results of this work indicate that it is the bound electron–hole pairs (excitons) that mainly contribute to gain in these lasers. However, the ratio of the number of free carriers to excitons is very important and significantly affects the threshold current and its temperature dependence. Our calculations show that the characteristic temperature T0 drops from 356 K when only excitons are included in the model, to a more realistic 83 K when both excitons and free carriers are considered.
Comparative current–voltage characteristics of nicked and repaired λ-DNA
Authors: Hartzell B. , McCord B. , Asare D. , Chen H. , Heremans J. J. , Soghomonian V.
Published: June 2003

We report on current–voltage characteristics obtained at room temperature on λ-DNA molecules, modified at both ends with disulfide groups and spanning Au electrodes. A comparison is drawn between the characteristics of the λ-DNA, which after modification features a gap between 3′ and 5′ sites (nicked DNA), and λ-DNA where this gap has been ligated (repaired DNA). The repaired DNA double helices show a close-to-linear current–voltage characteristic, and a dc conductivity estimated at ∼1×10−3 S cm−1. In contrast, the nicked DNA shows pronouncedly nonlinear and rectifying behavior, with a conductivity gap of ∼3 eV. The low-field conductivity of the nicked DNA is approximately a factor 20 lower than the repaired DNA’s conductivity.
Statistical evaluation of the Predictive Toxicology
Challenge 2000–2001
Authors: Toivonen Hannu , Srinivasan Ashwin , King Ross D. , Kramer Stefan , Helma Christoph
Published: June 2003

Motivation: The development of in silico models to predict chemical carcinogenesis from molecular structure would help greatly to prevent environmentally caused cancers. The Predictive Toxicology Challenge (PTC) competition was organized to test the state-of-the-art in applying machine learning to form such predictive models.

Results: Fourteen machine learning groups generated 111 models. The use of Receiver Operating Characteristic (ROC) space allowed the models to be uniformly compared regardless of the error cost function. We developed a statistical method to test if a model performs significantly better than random in ROC space. Using this test as criteria five models performed better than random guessing at a significance level p of 0.05 (not corrected for multiple testing). Statistically the best predictor was the Viniti model for female mice, with p value below 0.002. The toxicologically most interesting models were Leuven2 for male mice, and Kwansei for female rats. These models performed well in the statistical analysis and they are in the middle of ROC space, i.e. distant from extreme cost assumptions. These predictive models were also independently judged by domain experts to be among the three most interesting, and are believed to include a small but significant amount of empirically learned toxicological knowledge.

Availability: PTC details and data can be found at: http://www.predictive-toxicology.org/ptc/

Contact: hannu.toivonen@cs.helsinki.fi

* To whom correspondence should be addressed.
Calculation of helix packing angles in protein
structures
Authors: Dalton James A. R. , Michalopoulos Ioannis , Westhead David R.
Published: June 2003

Summary: Software is presented for the calculation of packing angles and geometry of helical secondary structure elements in protein structures.

Availability: C language source code and documentation is available from http://www.bioinformatics.leeds.ac.uk

Contact: D.R.Westhead@leeds.ac.uk

* To whom correspondence should be addressed.
A mathematical programming approach for
gene selection and tissue classification
Authors: Sun Minghe , Xiong Momiao
Published: June 2003

Motivation: Extracting useful information from expression levels of thousands of genes generated with microarry technology needs a variety of analytical techniques. Mathematical programming approaches for classification analysis outperform parametric methods when the data depart from assumptions underlying these methods. Therefore, a mathematical programming approach is developed for gene selection and tissue classification using gene expression profiles.

Results: A new mixed integer programming model is formulated for this purpose. The mixed integer programming model simultaneously selects genes and constructs a classification model to classify two groups of tissue samples as accurately as possible. Very encouraging results were obtained with two data sets from the literature as examples. These results show that the mathematical programming approach can rival or outperform traditional classification methods.

Contact: msun@utsa.edu

* To whom correspondence should be addressed.