bluuebunny/crossref_metadata_2025 huggingface dataset:
ELEMENTAL ANALYSIS AND SOURCE APPORTIONMENT OF AMBIENT PARTICULATE MATTER AT MASTERTON, NEW ZEALAND
Authors: DAVY P. , TROMPETTER W. J. , MARKWITZ A. , WEATHERBURN D. C.
Published: November 2005

At certain locations in the Wellington Region, pollution episodes due to air particulate matter are known to occur from time to time. Traditional gravimetric analysis of airborne particulate matter is unable to provide information on the sources contributing to air particulate concentrations. Ion Beam Analysis (IBA) is one of the few non-destructive techniques that can be used to identify the elemental composition of air particulate matter on a filter sample. In this work IBA was used to characterise air particulate matter in two size fractions, PM 20. and PM 10-2.0, collected at a monitoring station in Masterton, New Zealand. Elements with atomic mass above neon were measured by the PIXE technique. Elemental carbon was measured with a light reflectance device. Elemental 'fingerprints' of contributing sources were determined by performing factor analysis of the elemental composition. The results indicate that 'Sea Salt' and 'Soil' sources are major contributors to the coarse ( PM 10-2.0) fraction and 'Combustion' sources dominate the fine ( PM 2.0) fraction of air particulate matter. Analysis of seasonal differences was a useful tool in elucidating source profiles.
STOCHASTIC APPROACH TO DIVIDEND EQUALIZATION FUND MODELLING AND SOLVENCY
Authors: PETERSEN M. A. , RAUBENHEIMER H. , VAN DER WALT M.
Published: December 2005

In this contribution, the nonlinear dynamics of the surplus (net assets or reserve) process for a dividend-distributing company is studied in conjunction with the dynamics of its dividend equalization fund. The latter type of fund is maintained by leading insurance companies throughout the world and pays a special dividend for income that the investors lost because the dividend payment process was adversely affected for some or other reason. In our paper, a stochastic model for the related notion of a dividend equalization solvency ratio is derived. The ambient value of this ratio is an indication of the capacity of the insurer to pay dividends to shareholders especially when profit is low. The aforementioned analysis is, in turn, based on the construction of continuous time stochastic models for the dynamics of the surplus and total liabilities processes of an insurer. The discussions are reliant on principles arising within the asset-liability modelling paradigm.
ON THE WEAK-COUPLING LIMIT FOR BOSONS AND FERMIONS
Authors: BENEDETTO D. , PULVIRENTI M. , CASTELLA F. , ESPOSITO R.
Published: December 2005

In this paper we consider a large system of bosons or fermions. We start with an initial datum which is compatible with the Bose–Einstein, respectively Fermi–Dirac, statistics. We let the system of interacting particles evolve in a weak-coupling regime. We show that, in the limit, and up to the second order in the potential, the perturbative expansion expressing the value of the one-particle Wigner function at time t, agrees with the analogous expansion for the solution to the Uehling–Uhlenbeck equation.

This paper follows the same spirit as the companion work,2 where the authors investigated the weak-coupling limit for particles obeying the Maxwell–Boltzmann statistics: here, they proved a (much stronger) convergence result towards the solution of the Boltzmann equation.
DYNAMICS OF THE GROUND STATE AND CENTRAL VORTEX STATES IN BOSE–EINSTEIN CONDENSATION
Authors: BAO WEIZHU , ZHANG YANZHI
Published: December 2005

In this paper, we study dynamics of the ground state and central vortex states in Bose–Einstein condensation (BEC) analytically and numerically. We show how to define the energy of the Thomas–Fermi (TF) approximation, prove that the ground state is a global minimizer of the energy functional over the unit sphere and all excited states are saddle points in linear case, derive a second-order ordinary differential equation (ODE) which shows that time-evolution of the condensate width is a periodic function with/without a perturbation by using the variance identity, prove that the angular momentum expectation is conserved in two dimensions (2D) with a radial symmetric trap and 3D with a cylindrical symmetric trap for any initial data, and study numerically stability of central vortex states as well as interaction between a few central vortices with winding numbers ±1 by a fourth-order time-splitting sine-pseudospectral (TSSP) method. The merit of the numerical method is that it is explicit, unconditionally stable, time reversible and time transverse invariant. Moreover, it conserves the position density, performs spectral accuracy for spatial derivatives and fourth-order accuracy for time derivative, and possesses "optimal" spatial/temporal resolution in the semiclassical regime. Finally we find numerically the critical angular frequency for single vortex cycling from the ground state under a far-blue detuned Gaussian laser stirrer in strong repulsive interaction regime and compare our numerical results with those in the literatures.
MESTA — NON-INDUSTRIAL PRIVATE FOREST OWNERS' DECISION-SUPPORT ENVIRONMENT FOR THE EVALUATION OF ALTERNATIVE FOREST PLANS OVER THE INTERNET
Authors: PASANEN KARRI , KURTTILA MIKKO , PYKÄlÄINEN JOUNI , KANGAS JYRKI , LESKINEN PEKKA
Published: December 2005

The supply of Internet-based forest planning services to non-industrial private forest owners has increased. At the core of these services there is usually the "paper forest plan" in browseable format. The options to update the stand-level data and to download, fill and send various forms related to stand treatments are further characteristics of these services. The real potential of web-based services has not yet, however, been fully exploited. In addition, changes in the structure of non-industrial private forest ownership call for new facilities to be included in these services. The aim of this article is to present some characteristics that could be included in Internet-based forest planning services. The Mesta decision support service is intended to be used independently by forest owners, who are interested in examining, over the Internet, the production possibilities of their forest holding and in comparing alternative forest plans with respect to different goals concerning the use of their forest holding. Mesta includes a facility enabling preliminary objective enquiries from the forest owner, the creation and presentation of alternative forest plans and multi-criteria comparisons of alternative forest plans. The comparison technique is so executed that forest owners' independent assessments are enabled over the Internet without necessitating personal guidance by forest planning consultants. The results of trial use involving eight North-Karelian forest owners were encouraging. However, the current version of Mesta has been developed for research purposes and its properties and user-friendliness need to be improved before it can be included as a component of commercial Internet-based forest planning services.
Defect Evaluation of Spherical Silicon Solar Cells Fabricated by Dropping Method
Authors: Okamoto Chikao , Minemoto Takashi , Murozono Mikio , Takakura Hideyuki , Hamakawa Yoshihiro
Published: December 2005

Spherical Si solar cells are fabricated using polycrystalline Si spheres with a diameter of 1 mm produced by a high-speed dropping method. The distribution and types of electrically active defects in spherical Si solar cells have been directly characterized using electron-beam-induced current (EBIC) and transmission electron microscopy (TEM). Many recombination sink areas in grains and grain boundaries can be directly observed with EBIC in low-efficiency cells. The electrically active defects in grains are stronger recombination sinks than grain boundaries. The electrically active defect areas confirmed using EBIC were selectively etched with a Dash etching solution. TEM images revealed that the area showed a high dislocation density. These results suggest that the dislocations in grains deteriorate the performance of spherical Si solar cells.
Thermal Stability of Diamond Photodiodes Using Tungsten Carbide as Schottky Contact
Authors: Liao Meiyong , Alvarez Jose , Koide Yasuo
Published: December 2005

Deep-ultraviolet (DUV) photodiodes are fabricated using tungsten carbide (WC) Schottky and Ti/WC ohmic contacts on lightly boron-doped homoepitaxial diamond thin films. The thermal stability of the electrical and optical properties of the photodiodes upon isothermal annealing at 500°C for 5 h in argon/air ambient is demonstrated. The ideality factor is improved to unity after annealing for 1 h and increases to around 1.5 after subsequent annealing for longer time periods. The leakage current for at least 30 V reverse bias is lower than 10-14A before and after annealing for 4 h. The photoresponsivity at 220 nm is enhanced markedly by a factor of 103after annealing, resulting in a DUV/visible blind ratio as large as 106at 2 V reverse bias. In addition, the effects of annealing and applied bias on decay times and photoresponse spectra are examined, respectively. These results are discussed in terms of surface modification of the initially oxidized diamond epilayer.
Multiscale Analysis of Silicon Low-Pressure Chemical Vapor Deposition
Authors: Kinoshita Shigeru , Takagi Shigeyuki , Kai Tetsuya , Shiozawa Junichi , Maki Kunisuke
Published: December 2005

We consistently performed computer fluid dynamics (CFD) analysis in a reactor (macroscale analysis) and deposition profile analysis on a submicron hole (microscale analysis) for Si low-pressure chemical vapor deposition (LPCVD). For the gaseous phase and the surface reaction of the SiH4 source gas, we adopted the dominant reaction model, which involved two intermediates, SiH2 and Si2H6, and was based on the Kleijn Model. We analyzed the fluid flow, heat transfer and chemical reactions throughout the entire batch-type reactor, and estimated the Si growth rate, gaseous species concentration, and relative contributions of SiH4, SiH2 and Si2H6 to Si growth. Moreover, the Si-filling profile on a submicron hole was predicted by topography simulation in which the parameters were the growth rate, the relative contribution and the sticking coefficient of each species. The relationship between the relative contribution of SiH2, which has a high sticking coefficient, to Si growth and the hole-filling capability was quantitatively clarified from the results of a combination of the two analyses. The hole-filling capability at the wafer edge was deteriorated by the influence of SiH2 gas produced in the decomposition of Si2H6 gas, which was diffused from outside the wafer. This effect became considerable with increasing temperature. Reducing the wafer pitch will be effective in improving the hole-filling capability because both the SiH2 generation reaction in the region between wafers and SiH2 gas diffusion from outside the wafer will be inhibited.
Improvements on Electrical Characteristics of p-Channel Metal–Oxide–Semiconductor Field Effect Transistors with HfO2 Gate Stacks by Post Deposition N2O Plasma Treatment
Authors: Lu Wen-Tai , Chien Chao-Hsin , Lan Wen-Ting , Lee Tsung-Chieh , Yang Ming-Jui , Shen Shih-Wen , Lehnen Peer , Huang Tiao-Yuan
Published: December 2005

In this work, we found that employing a post deposition N2O plasma treatment following the deposition of HfO2 film can effectively improve the electrical characteristics of p-type channel metal–oxide–semiconductor field-effect transistors (pMOSFETs) with a HfO2 gate stack in terms of lower gate leakage current, lower interface state density, superior subthreshold swing, higher normalized transconductance and enhanced driving current even though it had led to a slightly higher equivalent oxide thickness (EOT) value of the HfO2 gate stack by around 0.3 nm. In order to clarify the attributes of the improvements, we used charge pumping (CP) measurement to analyze the densities of interface states and bulk traps in the HfO2 gate stacks. The improvements are then ascribed to the higher interface quality offered by the post deposition N2O plasma treatment. Moreover, we found that to more accurately estimate the bulk traps from the CP measurement, the leakage should be taken into account especially at low frequencies. Finally, it was found that the levels of the bulk traps and interface states can be reduced by the N2O plasma treatment, which also helps significantly eliminate the degradation of the gate stack during the subsequent voltage stress.
Materials Design for Cu Gettering by Electronic Dopants in Silicon
Authors: Michikita Toshiyuki , Shirai Koun , Katayama-Yoshida Hiroshi
Published: December 2005

In the silicon device process, there is a strong demand for eliminating copper contamination. Gettering of Cu by dopant atoms is a useful method for this purpose. In this paper, the gettering of Cu is theoretically studied. We have assessed the efficiency of gettering through the evaluation of the binding energies between Cu and electronic dopants and the dissociation energies. The calculated dissociation energies well describe the efficiency of various dopants, which have been found experimentally. It is shown that B and Al are the most efficient gettering centers among single dopants. The present study provides the basis for further study of the gettering mechanism and for the design of efficient gettering centers.
Growth Behavior of Nonpolar ZnO on M-plane and R-plane Sapphire by Metalorganic Vapor Phase Epitaxy
Authors: Moriyama Takumi , Fujita Shizuo
Published: December 2005

M-plane and A-plane ZnO films were grown on M-plane and R-plane sapphire substrates respectively. At high growth temperatures and/or VI/II ratios, ZnO grew along the direction perpendicular to the c-axis. On the other hand, at low growth temperatures and/or VI/II ratios, ZnO grew along the c-axis direction. A very smooth ZnO film was achieved on R-plane sapphire under a very low VI/II ratio condition. This was because the lateral growth was accelerated by a very strong tendency of growing along the c-axis. In contrast, on M-plane sapphire, C-plane ZnO nanorods tilted by 30° from the normal of the surface were formed under this growth condition.
Slow Group-Velocity Femtosecond Solitons in Dispersion Flattened Fiber
Authors: Chen Chi-Feng
Published: December 2005

The slow group-velocity femtosecond autosolitons in a dispersion flattened fiber are investigated, in which there is no third-order dispersion and there is no fourth-order dispersion. When the femtosecond pulse velocity is reduced to 50% of the normal group velocity, the analytical solutions of the bright and dark solitons are found. The magnitude of the fourth-order dispersion parameter is related to the high-order nonlinearity coefficient. The peak power and period of the solitons are determined by the magnitude of the fourth-order dispersion parameter and high-order nonlinearity coefficient.
Characterization of SiOx/Si/SiOx Coated n-InP Facets of Semiconductor Lasers Using Spatially-Resolved Photoluminescence
Authors: Lam S. K. K. , Cassidy Daniel T. , Mallard R. E.
Published: December 2005

Maps of the room temperature photoluminescence (PL) yield from SiO
x
/Si/SiO
x
coated semiconductor laser facets were made during the course of accelerated lifetesting. A localized degradation of the PL yield was detected under the active region after aging, which signifies a localized decrease of the radiative recombination efficiency. The surface reflectance was also investigated and was found to be uncorrelated with the localized degradation of the PL yield.
Nb-Doped SrTiO3-Based High-Temperature Schottky Solar Cells
Authors: Horikiri Fumimasa , Ichikawa Tomoyuki , Han Li Qun , Kaimai Atsushi , Yashiro Keiji , Matsumoto Hiroshige , Kawada Tatsuya , Mizusaki Junichiro
Published: December 2005

The high-temperature characteristics of donor-doped SrTiO3/indium tin oxide (ITO) Schottky solar cells were investigated by current–voltage and impedance analyses at various oxygen partial pressures (P
O2
) (1–10-4 bar) at 873 K. Both current–voltage and impedance characteristics showed a reversible oxygen partial pressure dependence. The junctions demonstrated the photovoltaic effect even at high temperatures, which means the nonohmic behavior of the heterojunction remains even at high temperatures. The highest open circuit voltage and short circuit current density were 123 mV and 1.37 mA cm-2, respectively, at 1 bar O2 under 261 mW cm-2 UV irradiation. Incident photon-to-current conversion efficiency and energy conversion efficiency improved as P
O2
increased. The influence of oxygen partial pressure on the solar cell characteristics is discussed.
Estimation of Parasitic Capacitance in Measurement of Hysteresis Properties of Ferroelectric Microcapacitors Using Scanning Probe Microscope
Authors: Okamura Soichiro , Iwase Takuma , Takeda Hiroaki , Nishida Takashi , Shiosaki Tadashi
Published: December 2005

Parasitic capacitances in the measurement of the hysteresis properties of ferroelectric microcapacitors are estimated. A scanning probe microscope with a conductive cantilever was used for contacting various-sized Pb(Zr,Ti)O3 (PZT) microcapacitors fabricated by electron-beam-induced patterning. A parasitic capacitance under the condition in which the cantilever was lifted up by 40 µm from the contact point was estimated to be 0.88 pF. Although all the PZT microcapacitors showed well-saturated hysteresis curves with compensation for the parasitic capacitance of 0.88 pF, the slopes of the compensated hysteresis curves around the maximum field increased with decreasing capacitor area. From the capacitor area dependence of the slopes, the increase in parasitic capacitance caused by bringing the cantilever near substrates for contact was estimated to be 0.049 pF. This increased parasitic capacitance evidently decreased the apparent coercive fields of the PZT microcapacitors with areas lower than 10 µm2 while it had no influence on remanent polarization.
A Novel Process to Control the Surface Roughness and Resistivity of Electroplated Cu Using Thiourea
Authors: Kang Moo Seong , Kim Soo-Kil , Kim Jae Jeong
Published: December 2005

Thiourea is a well-known additive in the electroplating industry due to its excellent ability to reduce surface roughness. However, sulfur dissociated from the thiourea is often incorporated into the plated Cu film as the byproduct CuS, which then increases the film's resistivity. The two-step Cu electroplating method proposed here deposited a smoother Cu surface film and matched the resistivity (after annealing) attained using methods that employ a thiourea-free electroplating of the Cu film. The Cu film obtained through two-step plating contained a sulfur concentration that was below the detection limit of Auger electron spectroscopy (AES).
Mapping Contact Potential Differences with Noncontact Atomic Force Microscope Using Resonance Frequency Shift versus Sample Bias Voltage Curves
Authors: Kitamura Shin'ichi , Yonei Kazunori , Iwatsuki Masashi , Mooney C. B. , Fukuda Yasuo
Published: December 2005

We have measured cantilever resonance frequency versus sample bias voltage and generated frequency vs bias ( f–V) curves using an ultrahigh-vacuum noncontact atomic force microscope (UHV NC-AFM). Using the f–V data, we calculated the contact potential difference (CPD) between the tip and the sample. These CPD measurements were compared with those that were directly observed with a scanning Kelvin probe force microscope (SKPM) on the same atomically resolved area of the sample using a UHV-AFM. The CPD values obtained by both methods were similar, however, it was difficult to obtain CPD values that agreed precisely on the atomic scale.
Synthesis of Cubic and Hexagonal CdTe Nanoparticles Dispersed in SiO2 Films: Role of Oxygen during Sintering
Authors: Dayal Padullaparthi Babu , Mehta Bodh Raj , Shivaprasad Sonnada M.
Published: December 2005

Cadmium telluride nanoparticles dispersed in SiO2 films have been grown by the co-sputtering of elemental Cd, Te and SiO2 targets in argon atmosphere. The role of oxygen during annealing on the structural and optical properties of CdTe nanoparticles dispersed in SiO2 films has been studied. Formation of a CdTeO3 layer around the CdTe nanoparticle core due to ambient oxygen present in air results in structural defects and thus the formation of hexagonal CdTe nanoparticles in air-annealed samples. In vacuum-annealed samples, defect free and well-crystallized cubic CdTe nanoparticles are formed which show excitonic features in the absorption spectra. These results have been confirmed by carrying out i) annealing in vacuum and air ambiences in a sequence on the same sample and ii) by depositing an additional layer of SiO2 on the CdTe:SiO2 samples to prevent the diffusion of ambient oxygen.
Effect of Ultrasound on Methanogenic Activity of Anaerobic Granules
Authors: Kim Youngwhan , Lee Jaekeun
Published: December 2005

For the first time, ultrasound was applied to enhance the activity of anaerobic granules. Specific methanogenic activity (SMA), carbohydrate and acetic acid analyses were performed to investigate how the limited intensity of ultrasound improves anaerobic digestion and activates methanogenic bacteria. The results of our study showed increases in SMA by 26 to 84% (St. Louis plant) and 163 to 220% (Newark plant) under the conditions of 50, 100, and 150 W for 5 min at a frequency of 40 kHz. The concentrations of soluble carbohydrates also increased 1.9 to 6.1 times as a result of ultrasound treatment.
Magnetic Anisotropy Study for GaMnAs-Based Magnetic Tunnel Junction
Authors: Uemura Tetsuya , Sone Takuya , Matsuda Ken-ichi , Yamamoto Masafumi
Published: December 2005

Magnetic anisotropy of GaMnAs/AlAs/GaMnAs magnetic tunnel junctions (MTJs) was investigated through tunnel magnetoresistance (TMR). The TMR ratio measured at 8 K for the fabricated MTJs took its maximum value of approximately 39% along the <100> direction, and decreased to about 19 and 10% in the [110] and [110] directions, respectively. This anisotropic TMR ratio suggests that the cubic magnetic anisotropy with its easy axis along the <100> directions is dominant, whereas the uniaxial anisotropy with its easy axis along the [110] direction slightly exists. The domain-wall displacement model, rather than the coherent rotation model, accurately explained the angular dependences of both the switching field and the TMR ratios. Temperature dependences of anisotropic TMR ratios revealed that lower than 25 K the maximum TMR ratio was obtained along the <100> directions, whereas higher than 25 K the maximum was obtained along the [110] direction, indicating crossover of the easy axis directions.
Effect of MnO2 on the Piezoelectric Properties of (1-x)(Na0.5K0.5)NbO3–xBaTiO3 Ceramics
Authors: Ahn Cheol-Woo , Song Hyun-Cheol , Nahm Sahn , Park Seung-Ho , Uchino Kenji , Priya Shashank , Lee Hyeung-Gyu , Kang Nam-Kee
Published: December 2005

(Na0.5K0.5)NbO3 (NKN) and BaTiO3 (BT) ceramics form a homogeneous solid solution. The relative density of the (1-x)NKN–xBT solid solutions significantly decreased when x≤0.07. Although the relative density of the 0.95NKN–0.05BT ceramic was very low, it had a high d
33 value of 134 pC/N. MnO2 was added to improve the piezoelectric properties of the 0.95NKN–0.05BT ceramics by enhancing their sinterability. The addition of MnO2 increased the density of the specimens, as well as improving the piezoelectric properties. The 0.9 mol % MnO2 added 0.95NKN–0.05BT ceramics showed the good piezoelectric properties of k
p=0.31, d
33=194 pC/N and ε
3
T/ ε
0 = 800.
Efficient Observation of Narrow Isolated Photoluminescence Spectra from Spatially Localized Excitons in InGaN Quantum Wells
Authors: Gotoh Hideki , Akasaka Tetsuya , Tawara Takehiko , Kobayashi Yasuyuki , Makimoto Toshiki , Nakano Hidetoshi
Published: December 2005

We report discrete photoluminescence (PL) spectra with narrow linewidths from spatially localized excitons obtained in InGaN quantum wells (QWs) that are of a similar structure to those used in conventional optical devices. A micro-PL measurement combined with submicrometer-scale fabrication techniques allows us to create a small number of excitons in a laser spot and to detect the PL from single spatially localized excitons. A sharp PL line (linewidth: 0.34 meV limited by the resolution) is clearly obtained in a 0.2 µm mesa-shaped QW, which originates from a single localized exciton. We show that the technique is a more powerful method of examining excitonic effects than previously reported methods.
Temperature and Electric Field Dependences of Optical Damage in Proton-Exchanged Waveguides Formed on MgO-Doped Lithium Niobate Crystals
Authors: Ikeda Akira , Oi Takanori , Nakayama Kazuhiko , Otsuka Yukiko , Fujii Yoichi
Published: December 2005

The temperature and electric field dependences of the photorefractive effect in proton-exchanged (PE) waveguides formed on MgO-doped lithium niobate (LN) are investigated in detail for the first time. As a result, the photorefractive effect (optical damage) is found to be enhanced by the electric field applied to the waveguide. On the other hand, resistance to the photorefractive effect is markedly increased when the samples are heated at temperatures as high as 80°C. We should take these properties into consideration in designing optical devices such as electrooptic modulators and parametric devices.
Fabrication of Fluorescence Micropatterns to Photoresists by Selective Doping of Fluorescent Dye Using Vapor Transportation Method
Authors: Mizokuro Toshiko , Mochizuki Hiroyuki , Tanigaki Nobutaka , Mo Xiaoliang , Yamamoto Noritaka , Hiraga Takashi
Published: December 2005

We report a novel patterning process that adds fluorescence to a positive-type photoresist by doping vapor of the fluorescent dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)4H-pyran (DCM), using a simple vacuum process called vapor transportation method. DCM-doped photoresist films were examined by UV-vis absorption spectroscopy, fluorescent spectroscopy, and optical microscopy. When DCM vapor was used to dope unexposed films at temperatures above 140°C, absorption and fluorescence peaks due to DCM were detected. In contrast, when DCM vapor was used to dope exposed films, no absorption and only weak fluorescence peaks were detected. These results indicated the selective doping of DCM vapor into unexposed photoresist films. When DCM vapor reached the surfaces of micropatterned photoresist films with both unexposed and exposed areas, DCM was doped selectively into the unexposed areas of the films, resulting in the production of micropatterns with DCM molecules in the patterned films.
Comparison of Ge and GaAs Substrates for Metalorganic Vapor Phase Epitaxy of GaIn(N)As Quantum Wells
Authors: Knuuttila Lauri , Reentilä Outi , Mattila Marco , Lipsanen Harri
Published: December 2005

Comparison of Ge and GaAs substrates for the growth of InGaAs and GaInNAs quantum well structures is presented. Quantum well structures are grown simultaneously on both substrates by metalorganic vapor phase epitaxy. Photoluminescence measurements show lower peak energies for the structures grown on Ge than on GaAs. The luminescence redshift between structures grown on Ge and GaAs increases with increasing nitrogen precursor flow. X-ray diffraction analyses indicate that this is due to enhanced N incorporation efficiency on Ge.
GaN Heteroepitaxial Growth on LiTaO3(0001) Step Substrates by Pulsed Laser Deposition
Authors: Tsuchiya Yousuke , Kobayashi Atsushi , Ohta Jitsuo , Fujioka Hiroshi , Oshima Masaharu
Published: December 2005

We grew GaN epitaxial films on LiTaO3 by pulsed laser deposition (PLD) for the first time and investigated their structural properties. Atomically flat surfaces can be achieved on the LiTaO3 substrates by annealing at 1050°C in a box made of LiNbO3. We found that GaN(0001) grows epitaxially on these atomically flat LiTaO3(0001) substrates at substrate temperatures ranging from 580 to 700°C, with an in-plane epitaxial relationship of GaN[1010]∥LiTaO3[1120]. X-ray reflectivity measurements revealed that the thickness of the interfacial layer between GaN and LiTaO3 decreases from 1.9 to 0.4 nm by reducing the growth temperature from 700 to 580°C. We used GaN films grown at 580°C as buffer layers for the growth of GaN films at 700°C, and found that the crystalline quality and the surface morphology of these films were improved by the use of the low-temperature buffer layer.
Impaired trafficking of choline transporter-like protein-1 at plasma membrane and inhibition of choline transport in THP-1 monocyte-derived macrophages
Authors: Fullerton Morgan D. , Wagner Laura , Yuan Zongfei , Bakovic Marica
Published: December 2005

The present study investigates choline transport processes and regulation of choline transporter-like protein-1 (CTL1) in human THP-1 monocytic cells and phorbol myristate 13-acetate (PMA)-differentiated macrophages. Choline uptake is saturable and therefore protein-mediated in both cell types, but its transport characteristics change soon after treatments with PMA. The maximal rate of choline uptake intrinsic to monocytic cells is greatly diminished in differentiated macrophages as demonstrated by alterations in Vmaxvalues from 1,973 ± 118 to 380 ± 18 nmol·mg−1·min−1, when the binding affinity did not change significantly ( Kmvalues 56 ± 8 and 53 ± 6 μM, respectively). Treatments with hemicholinim-3 effectively inhibit most of the choline uptake, establishing that a choline-specific transport protein rather than a general transporter is responsible for the observed kinetic parameters. mRNA screening for the expression of various transporters reveals that CTL1 is the most plausible candidate that possesses the described kinetic and inhibitory properties. Fluorescence-activated cell sorting analyses at various times after PMA treatments further demonstrate that the disappearance of CTL1 protein from the cell surface follows the same trend as the reduction in choline uptake. Importantly, the loss of functional CTL1 from the cell surface occurs without significant changes in total CTL1 protein or its mRNA level indicating that an impaired CTL1 trafficking is the key contributing factor to the reduced choline uptake, subsequent to the PMA-induced THP-1 differentiation to macrophages.
Autofeedback effects of progressively rising oxytocin concentrations on supraoptic oxytocin neuronal activity in slices from lactating rats
Authors: Wang Yu-Feng , Ponzio Todd A. , Hatton Glenn I.
Published: December 2005

Suckling stimuli induce somatodendritic oxytocin (OT) release from supraoptic nucleus (SON) neurons, which raises intranuclear OT concentrations and contributes to the effectiveness of the milk-ejection reflex. To clarify how such changes in OT concentrations modulate the activity of OT neurons, we examined OT effects using whole cell patch-clamp recordings from SON neurons in slices from lactating rats. Progressive increases from extremely low OT concentrations (0.1–10 fM) to high concentrations (0.1–10 nM) induced excitation and subsequent spike frequency reduction (SFR) in OT neurons. Significant effects of OT on firing rates were observed starting at 1 fM, reached peak level from 1 fM to 1 pM before SFR occurred in most neurons. The buildup of OT concentrations progressively promoted depolarization of membrane potential, spike broadening, decreases in spike amplitude, and increases in the rise time of spike afterhyperpolarizations, which were unrelated to firing rate. However, intermittent application of OT (1 fM, 1 pM, and 1 nM, each for 5 min) evoked dose-dependent excitation but not the SFR. Application of 1 pM OT for 40 min simulated the effects of progressively increasing OT concentrations. Vasopressin neurons were also activated by OT but did not show SFR. Consistent with presynaptic loci of OT action, ionotropic glutamate receptor antagonists reduced OT effects on firing rate, whereas bicuculline did not change the excitatory effects. These results suggest that the specific autoregulatory effects of OT, and perhaps other neuropeptides as well, are time and concentration dependent.
Canal and Otolith Contributions to Visual Orientation Constancy During Sinusoidal Roll Rotation
Authors: Kaptein Ronald G. , Van Gisbergen Jan A.M.
Published: December 2005

Using vestibular sensors to maintain visual stability during changes in head tilt, crucial when panoramic cues are not available, presents a computational challenge. Reliance on the otoliths requires a neural strategy for resolving their tilt/translation ambiguity, such as canal–otolith interaction or frequency segregation. The canal signal is subject to bandwidth limitations. In this study, we assessed the relative contribution of canal and otolith signals and investigated how they might be processed and combined. The experimental approach was to explore conditions with and without otolith contributions in a frequency range with various degrees of canal activation. We tested the perceptual stability of visual line orientation in six human subjects during passive sinusoidal roll tilt in the dark at frequencies from 0.05 to 0.4 Hz (30° peak to peak). Because subjects were constantly monitoring spatial motion of a visual line in the frontal plane, the paradigm required moment-to-moment updating for ongoing ego motion. Their task was to judge the total spatial sway of the line when it rotated sinusoidally at various amplitudes. From the responses we determined how the line had to be rotated to be perceived as stable in space. Tests were taken both with (subject upright) and without (subject supine) gravity cues. Analysis of these data showed that the compensation for body rotation in the computation of line orientation in space, although always incomplete, depended on vestibular rotation frequency and on the availability of gravity cues. In the supine condition, the compensation for ego motion showed a steep increase with frequency, compatible with an integrated canal signal. The improvement of performance in the upright condition, afforded by graviceptive cues from the otoliths, showed low-pass characteristics. Simulations showed that a linear combination of an integrated canal signal and a gravity-based signal can account for these results.
Neurons in the Medial Nucleus of the Trapezoid Body and Superior Paraolivary Nucleus of the Rat May Play a Role in Sound Duration Coding
Authors: Kadner Alexander , Kulesza Randy J. , Berrebi Albert S.
Published: December 2005

We describe neurons in two nuclei of the superior olivary complex that display differential sensitivities to sound duration. Single units in the medial nucleus of the trapezoid body (MNTB) and superior paraolivary nucleus (SPON) of anesthetized rats were studied. MNTB neurons produced primary-like responses to pure tones and displayed a period of suppressed spontaneous activity after stimulus offset. In contrast, neurons of the SPON, which receive a strong glycinergic input from MNTB, showed very little or no spontaneous activity and responded with short bursts of action potentials after the stimulus offset. Because SPON spikes were restricted to the same time window during which suppressed spontaneous activity occurs in the MNTB, we presume that SPON offset activity represents a form of postinhibitory rebound. Using characteristic frequency tones of 2- to 1,000-ms duration presented 20 dB above threshold, we show that the profundity and duration of the suppression of spontaneous activity in MNTB as well as the magnitude and first spike latency of the SPON offset response depend on stimulus duration as well as on stimulus intensity, showing a tradeoff between intensity and duration. Pairwise comparisons of the responses to stimuli of various durations revealed that the duration sensitivity in both nuclei is sharpest for stimuli <50 ms.
Olfactory Nerve Stimulation-Induced Calcium Signaling in the Mitral Cell Distal Dendritic Tuft
Authors: Yuan Q. , Knöpfel T.
Published: December 2005

Olfactory receptor neuron axons form the olfactory nerve (ON) and project to the glomerular layer of the olfactory bulb, where they form excitatory synapses with terminal arborizations of the mitral cell (MC) tufted primary dendrite. Clusters of MC dendritic tufts define olfactory glomeruli, where they involve in complex synaptic interactions. The computational function of these cellular interactions is not clear. We used patch-clamp electrophysiology combined with whole field or two-photon Ca2+ imaging to study ON stimulation-induced Ca2+ signaling at the level of individual terminal branches of the MC primary dendrite in mice. ON-evoked subthreshold excitatory postsnaptic potentials induced Ca2+ transients in the MC tuft dendrites that were spatially inhomogeneous, exhibiting discrete “hot spots.” In contrast, Ca2+ transients induced by backpropagating action potentials occurred throughout the dendritic tuft, being larger in the thin terminal dendrites than in the base of the tuft. Single ON stimulation-induced Ca2+ transients were depressed by the NMDA receptor antagonist d-aminophosphonovaleric acid (d-APV), increased with increasing stimulation intensity, and typically showed a prolonged rising phase. The synaptically induced Ca2+ signals reflect, at least in part, dendrodendritic interactions that support intraglomerular coupling of MCs and generation of an output that is common to all MCs associated with one glomerulus.
Divergence between motoneurons: gene expression profiling provides a molecular characterization of functionally discrete somatic and autonomic motoneurons
Authors: Cui Dapeng , Dougherty Kimberly J. , Machacek David W. , Sawchuk Michael , Hochman Shawn , Baro Deborah J.
Published: November 2005

Studies in the developing spinal cord suggest that different motoneuron (MN) cell types express very different genetic programs, but the degree to which adult programs differ is unknown. To compare genetic programs between adult MN columnar cell types, we used laser capture microdissection (LCM) and Affymetrix microarrays to create expression profiles for three columnar cell types: lateral and medial MNs from lumbar segments and sympathetic preganglionic motoneurons located in the thoracic intermediolateral nucleus. A comparison of the three expression profiles indicated that ∼7% (813/11,552) of the genes showed significant differences in their expression levels. The largest differences were observed between sympathetic preganglionic MNs and the lateral motor column, with 6% (706/11,552) of the genes being differentially expressed. Significant differences in expression were observed for 1.8% (207/11,552) of the genes when comparing sympathetic preganglionic MNs with the medial motor column. Lateral and medial MNs showed the least divergence, with 1.3% (150/11,552) of the genes being differentially expressed. These data indicate that the amount of divergence in expression profiles between identified columnar MNs does not strictly correlate with divergence of function as defined by innervation patterns (somatic/muscle vs. autonomic/viscera). Classification of the differentially expressed genes with regard to function showed that they underpin all fundamental cell systems and processes, although most differentially expressed genes encode proteins involved in signal transduction. Mining the expression profiles to examine transcription factors essential for MN development suggested that many of the same transcription factors participate in combinatorial codes in embryonic and adult neurons, but patterns of expression change significantly.
Identification of novel transcriptional networks in response to treatment with the anticarcinogen 3H-1,2-dithiole-3-thione
Authors: Huang Yong , Yan Jian , Lubet Ronald , Kensler Thomas W. , Sutter Thomas R.
Published: November 2005

3 H-1,2-dithiole-3-thione (D3T), an inducer of antioxidant and phase 2 genes, is known to enhance the detoxification of environmental carcinogens, prevent neoplasia, and elicit other protective effects. However, a comprehensive view of the regulatory pathways induced by this compound has not yet been elaborated. Fischer F344 rats were gavaged daily for 5 days with vehicle or D3T (0.3 mmol/kg). The global changes of gene expression in liver were measured with Affymetrix RG-U34A chips. With the use of functional class scoring, a semi-supervised method exploring both the expression pattern and the functional annotation of the genes, the Gene Ontology classes were ranked according to the significance of the impact of D3T treatment. Two unexpected functional classes were identified for the D3T treatment, cytosolic ribosome constituents with 90% of those genes increased, and cholesterol biosynthesis with 91% of the genes repressed. In another novel approach, the differentially expressed genes were evaluated by the Ingenuity computational pathway analysis tool to identify specific regulatory networks and canonical pathways responsive to D3T treatment. In addition to the known glutathione metabolism pathway ( P = 0.0011), several other significant pathways were also revealed, including antigen presentation ( P = 0.000476), androgen/estrogen biosynthesis ( P = 0.000551), fatty acid ( P = 0.000216), and tryptophan metabolism ( P = 0.000331) pathways. These findings showed a profound impact of D3T on lipid metabolism and anti-inflammatory/immune-suppressive response, indicating a broader cytoprotective effect of this compound than previously expected.
Carcinoembryonic Antigen–Related Cell Adhesion Molecule 1a-4L Suppression of Rat Hepatocellular Carcinomas
Authors: Laurie Nikia A. , Comegys Meghan M. , Carreiro Marie P. , Brown Jeanne F. , Flanagan Donna L. , Brilliant Kate E. , Hixson Douglas C.
Published: December 2005

Carcinoembryonic antigen (CEA)–related cell adhesion molecule 1 (CEACAM1) is a member of the CEA family of immunoglobulin-like adhesion molecules with two major splice variants, CEACAM1a-4L and CEACAM1b-4S, differing in the length of their COOH-terminal cytoplasmic tail. Both forms are down-regulated in prostate and liver carcinomas relative to normal tissues. We have previously shown in a nude mouse xenograft model that restoration of CEACAM1a-4L expression in human prostate carcinoma cells (PC-3) suppresses tumorigenicity, an effect observed with carcinomas from several other tissues but never established for hepatocellular carcinomas. In this report, we have examined the effect of CEACAM1a-4L on tumorigenicity of 1682A, a rat hepatocellular carcinoma that grows on the omentum when injected into the peritoneal cavity. Results show that restoration of CEACAM1a-4L expression at levels 13- and 0.45-fold compared with negative controls or normal hepatocytes, respectively, completely suppressed the formation of 1682A tumor nodules on the omentum at 3 weeks after injection. In contrast, 1682A cells infected with CEACAM1b-4S or an empty retroviral vector formed multiple clusters of tumor nodules. Although tumor nodules of 1682A cells positive and negative for CEACAM1a-4L did not display significant differences in histologic organization, aggregates formed in vitro by 1682A-L were smaller in size and displayed enlarged intercellular spaces relative to their 1682A-V counterparts. Restoration of CEACAM1a-4L expression did not elevate levels of apoptosis but seemed to cause an increase in the length of G1. This is the first demonstration of CEACAM1a-4L–induced tumor suppression in liver carcinomas using a quantifiable i.p. syngeneic transplantation model.
Phosphorylation of Galectin-3 Contributes to Malignant Transformation of Human Epithelial Cells via Modulation of Unique Sets of Genes
Authors: Mazurek Nachman , Sun Yun Jie , Price Janet E. , Ramdas Latha , Schober Wendy , Nangia-Makker Pratima , Byrd James C. , Raz Avraham , Bresalier Robert S.
Published: December 2005

Galectin-3 is a multifunctional β-galactoside-binding protein implicated in apoptosis, malignant transformation, and tumor progression. The mechanisms by which galectin-3 contributes to malignant progression are not fully understood. In this study, we found that the introduction of wild-type galectin-3 into nontumorigenic, galectin-3-null BT549 human breast epithelial cells conferred tumorigenicity and metastatic potential in nude mice, and that galectin-3 expressed by the cells was phosphorylated. In contrast, BT549 cells expressing galectin-3 incapable of being phosphorylated (Ser6→Glu Ser6→Ala) were nontumorigenic. A microarray analysis of 10,000 human genes, comparing BT549 transfectants expressing wild-type and those expressing phosphomutant galectin-3, identified 188 genes that were differentially expressed (>2.5-fold). Genes affected by introduction of wild-type phosphorylated but not phosphomutant galectin-3 included those involved in oxidative stress, a novel noncaspase lysosomal apoptotic pathway, cell cycle regulation, transcriptional activation, cytoskeleton remodeling, cell adhesion, and tumor invasion. The reliability of the microarray data was validated by real-time reverse transcription-PCR (RT-PCR) and by Western blot analysis, and clinical relevance was evaluated by real-time RT-PCR screening of a panel of matched pairs of breast tumors. Differentially regulated genes in breast cancers that are also predicted to be associated with phospho-galectin-3 in transformed BT549 cells include C-type lectin 2, insulin-like growth factor-binding protein 5, cathepsins L2, and cyclin D1. These data show the functional diversity of galectin-3 and suggest that phosphorylation of the protein is necessary for regulation (directly or indirectly) of unique sets of genes that play a role in malignant transformation.
E1AF/PEA3 Activates the Rho/Rho-Associated Kinase Pathway to Increase the Malignancy Potential of Non–Small-Cell Lung Cancer Cells
Authors: Hakuma Nobuyuki , Kinoshita Ichiro , Shimizu Yasushi , Yamazaki Koichi , Yoshida Koichi , Nishimura Masaharu , Dosaka-Akita Hirotoshi
Published: December 2005

E1AF/PEA3, an Ets family transcription factor, is frequently overexpressed in non–small-cell lung cancers (NSCLCs). Overexpression of E1AF increases motility and invasion of VMRC-LCD and NCI-H226 NSCLC cells, which lack endogenous E1AF expression, and the effect is synergistically increased by hepatocyte growth factor (HGF). The small GTPase Rho/Rho-associated kinase (ROCK) pathway is also involved in motility and invasion. To determine the role of the Rho/ROCK pathway in malignant phenotypes induced by E1AF, we analyzed VMRC-LCD cells transfected with an E1AF expression vector (LCD-E1AF cells) or with empty vector (LCD-vector cells). LCD-E1AF cells had more GTP-bound (active) Rho than LCD-vector cells and Rho activation was synergistically increased by HGF. The Rho activation by E1AF and HGF was also shown in NCI-H226 cells. Phosphorylation of myosin light chain (MLC), a downstream effector of ROCK signaling, was higher in LCD-E1AF cells than in LCD-vector cells, especially under HGF treatment. A specific ROCK inhibitor, Y27632, strongly suppressed MLC phosphorylation, cell motility, and invasion. In nude mice implanted s.c. and intrapulmonarily, LCD-E1AF cells made more local tumors than LCD-vector cells (six of six versus one of seven mice and four of seven versus one of seven mice, respectively). Three of the four mice with lung tumors from LCD-E1AF cells had lymph node metastases whereas the mouse with LCD-vector tumors did not. LCD-E1AF tumors showed higher MLC phosphorylation than LCD-vector tumors. These results suggest that E1AF activates the Rho/ROCK pathway in an HGF-enhanced manner and its activation is important in E1AF-induced motility and invasion as well as tumorigenesis and metastasis in NSCLC cells.