bluuebunny/crossref_metadata_2025 huggingface dataset:
Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts
Authors: Comini E. , Faglia G. , Sberveglieri G. , Pan Zhengwei , Wang Zhong L.
Published: August 2002

Gas sensors have been fabricated using the single-crystalline SnO2 nanobelts. Electrical characterization showed that the contacts were ohmic and the nanobelts were sensitive to environmental polluting species like CO and NO2, as well as to ethanol for breath analyzers and food control applications. The sensor response, defined as the relative variation in conductance due to the introduction of the gas, is 4160% for 250 ppm of ethanol and −1550% for 0.5 ppm NO2 at 400 °C. The results demonstrate the potential of fabricating nanosized sensors using the integrity of a single nanobelt with a sensitivity at the level of a few ppb.
Spinodal decomposition range of InxGa1−xNyAs1−y alloys
Authors: Asomoza R. , Elyukhin V. A. , Peña-Sierra R.
Published: August 2002

Spinodal decomposition range of InxGa1−xNyAs1−y quaternary alloys as the result of the strain and coherency strain energies, transformations of the bonds, and a lattice mismatch between the GaAs substrate and an alloy is described. The alloys are considered in the strictly regular approximation. The strain energy is presented in the valence-force field model. The spinodal decomposition temperatures of InxGa1−xNyAs1−y alloys are demonstrated up to 1000 °C. It is shown that nitrogen dramatically increases the temperature of the coherent spinodal.
Electronic properties of vacancy–oxygen complex in Ge crystals
Authors: Markevich V. P. , Hawkins I. D. , Peaker A. R. , Litvinov V. V. , Murin L. I. , Dobaczewski L. , Lindström J. L.
Published: August 2002

It is argued that the vacancy–oxygen (VO) complex (A center) in Ge has three charge states: double negative, single negative, and neutral. Corresponding energy levels are located at Ec−0.21 eV (VO−−/−) and Ev+0.27 eV (VO−/0). An absorption line at 716 cm−1 has been assigned to the asymmetrical stretching vibration mode of the doubly negatively charged VO complex.
Interface structures generated by negative-bias temperature instability in Si/SiO2 and Si/SiOxNy interfaces
Authors: Ushio Jiro , Maruizumi Takuya , Kushida-Abdelghafar Keiko
Published: August 2002

We used a density functional method to investigate the mechanism of negative-bias temperature instability (NBTI) and resultant structural changes of Si/SiO2 and Si/SiOxNy interfaces. The reaction energies for the water- and hydrogen-originated instabilities of several interface defects show that water-originated reactions of oxygen and nitrogen vacancies occur most easily. The larger instability of the Si/SiOxNy interface, compared with the Si/SiO2 interface, can be understood in terms of the difference in reaction energies. According to the calculated nitrogen 1s core-level shifts of the nitrogen atoms at the Si/SiOxNy interface, it is possible to identify a NBTI-generated structure at the Si/SiOxNy interface by x-ray photoelectron spectroscopy.
Low-stress indium–tin–oxide thin films rf magnetron sputtered on polyester substrates
Authors: Carcia P. F. , McLean R. S. , Reilly M. H. , Li Z. G. , Pillione L. J. , Messier R. F.
Published: August 2002

Using rf magnetron sputtering, we have grown low resistivity (∼3×10−4 Ω cm), high transparency (>80%) indium–tin–oxide thin films with near zero stress on polyester substrates, near room temperature. We concluded from analysis of sputtered ions and atoms that bombardment by energetic (>70 eV) negative oxygen ions caused high stress (∼1 GPa) in films grown at lower (6 mTorr) pressure. Sputtering at 12 mTorr dissipated energetic bombardment and reduced film stress to about zero, independent of oxygen partial pressure (pO2). However, increasing pO2 did affect film microstructure, that is, crystallinity, roughness, and grain size.
Characterization of homoepitaxial p-type ZnO grown by molecular beam epitaxy
Authors: Look D. C. , Reynolds D. C. , Litton C. W. , Jones R. L. , Eason D. B. , Cantwell G.
Published: August 2002

An N-doped, p-type ZnO layer has been grown by molecular beam epitaxy on an Li-diffused, bulk, semi-insulating ZnO substrate. Hall-effect and conductivity measurements on the layer give: resistivity=4×101 Ω cm; hole mobility=2 cm2/V s; and hole concentration=9×1016 cm−3. Photoluminescence measurements in this N-doped layer show a much stronger peak near 3.32 eV (probably due to neutral acceptor bound excitons), than at 3.36 eV (neutral donor bound excitons), whereas the opposite is true in undoped ZnO. Calibrated, secondary-ion mass spectroscopy measurements show an N surface concentration of about 1019 cm−3 in the N-doped sample, but only about 1017 cm−3 in the undoped sample.
Dual behavior of H+ at Si–SiO2 interfaces: Mobility versus trapping
Authors: Rashkeev S. N. , Fleetwood D. M. , Schrimpf R. D. , Pantelides S. T.
Published: August 2002

We report first-principles calculations showing that protons in the vicinity of a Si–SiO2 interface can behave in two different ways. At an abrupt interface without suboxide bonds (Si–Si bonds at the oxide side of the interface) H+ does not become trapped but migrates laterally until it reacts with a point defect (e.g., depassivates a hydrogenated dangling bond). On the other hand, when large concentrations of suboxide bonds are present, H+ can become trapped in a deep energy minimum with a highly asymmetric energy barrier. Thus, large H+ densities first saturate suboxide bonds, and the balance can be cycled back and forth between a pair of interfaces by reversing the electric field. These results account for the experimentally observed dual behavior of protons at Si–SiO2 interfaces.
Scaling quantum-dot light-emitting diodes to submicrometer sizes
Authors: Fiore A. , Chen J. X. , Ilegems M.
Published: August 2002

We introduce a device structure and a fabrication technique that allow the realization of efficient light-emitting diodes (LEDs) with dimensions of the active area in the ≈100 nm range. Using optical lithography, selective oxidation, and an active region consisting of InAs quantum dots (QDs), we fabricated LEDs with light–current–voltage characteristics which scale well with nominal device area down to 600 nm diam at room temperature. The scaling behavior provides evidence for strong carrier confinement in the QDs and shows the potential for the realization of high-efficiency single-photon LEDs operating at room temperature.
Large g-factor enhancement in high-mobility InAs/AlSb quantum wells
Authors: Sadofyev Yu. G. , Ramamoorthy A. , Naser B. , Bird J. P. , Johnson S. R. , Zhang Y.-H.
Published: August 2002

We discuss the growth by molecular-beam epitaxy, and studies of the low-temperature electrical properties, of undoped InAs/AlSb quantum wells. The two-dimensional electron gas realized in the wells exhibits high mobility at low temperatures, and an analysis of its Shubnikov–de Haas oscillations suggests this mobility is limited by scattering from remotely located unintentional dopants. Spin splitting of the oscillations is clearly resolved at 4.2 K, revealing a g-factor as large as −60 at high magnetic fields. The size of this enhancement increases with decreasing electron density, and is thought to reflect the associated increase in the strength of the effective Coulomb interaction.
Determination of the next-nearest neighbor order in β phase in Cu-Al-Ni shape memory alloys
Authors: Pérez-Landazábal J. I. , Recarte V. , Pérez-Sáez R. B. , Nó M. L. , Campo J. , San Juan J.
Published: August 2002

The metastable β phase undergoes two order–disorder transitions during quenching from high temperature in Cu-based shape memory alloys. First, it undergoes a B2 ordering at nearest neighbors and then a second one at next-nearest neighbors that has not been clearly established. Neutron powder diffraction measurements have been performed at room temperature in a fully ordered alloy (Cu-27.4 Al-3.6 Ni at. %). Rietveld analysis allows to conclude that a L21 order at next-nearest neighbors is present in the ordered phase. The site occupancy of the different positions has been determined.
Hydrogen-induced degradation in ferroelectric Bi3.25La0.75Ti3O12
Authors: Seo Sunae , Yoon Jong-Gul , Kim J. D. , Song T. K. , Kang B. S. , Noh T. W. , Lee Y. K. , Kim Ch. J. , Lee I. S. , Lee J. K. , Park Y. S.
Published: August 2002

Effects of forming gas annealing (FGA) were investigated on ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films fabricated by a chemical solution deposition. With the FGA up to 350 °C, the Pt/BLT/Pt capacitors showed good ferroelectric characteristics without significant degradation. As the FGA temperature was increased, a decomposition of the BLT powder sample was observed by using thermogravimetric analysis. By comparing the time-dependent weight loss of BLT with that of Bi4Ti3O12 during FGA, La doping was found to significantly impede the decomposition rate. The decomposition, especially in the (Bi2O2)2+ layers, was discussed as a hydrogen-induced degradation mechanism in the Bi-layered perovskite ferroelectrics.
Enhanced hole injections in organic light-emitting devices by depositing nickel oxide on indium tin oxide anode
Authors: Chan I-Min , Hsu Tsung-Yi , Hong Franklin C.
Published: August 2002

An ultrathin layer of nickel oxide (NiO) was deposited on the indium tin oxide (ITO) anode to enhance the hole injections in organic light-emitting diode (OLED) devices. A very low turn-on voltage (3 V) was actually observed for the device with NiO on ITO. The enhancement of hole injections by depositing NiO on the ITO anode was further verified by the hole-only devices. The excellent hole-injection ability of NiO was also demonstrated by devising a device with patterned NiO on the ITO anode. Our results suggest that the NiO/ITO anode is an excellent choice to enhance hole injections of OLED devices.
Simulation of chemical mechanical planarization of copper with molecular dynamics
Authors: Ye Y. , Biswas R. , Bastawros A. , Chandra A.
Published: August 2002

With an aim to understanding the fundamental mechanisms underlying chemical mechanical planarization (CMP) of copper, we simulate the nanoscale polishing of a copper surface with molecular dynamics utilizing the embedded atom method. Mechanical abrasion produces rough planarized surfaces with a large chip in front of the abrasive particle, and dislocations in the bulk of the crystal. The addition of chemical dissolution leads to very smooth planarized copper surfaces and considerably smaller frictional forces that prevent the formation of bulk dislocations. This is a first step towards understanding the interplay between mechanistic material abrasion and chemical dissolution in chemical mechanical planarization of copper interconnects.
Record number (11 000) of interference fringes obtained by a 1 MV field-emission electron microscope
Authors: Akashi Tetsuya , Harada Ken , Matsuda Tsuyoshi , Kasai Hiroto , Tonomura Akira , Furutsu Tadao , Moriya Noboru , Yoshida Takaho , Kawasaki Takeshi , Kitazawa Koichi , Koinuma Hideomi
Published: August 2002

An electron biprism for a 1 million-volt field-emission electron microscope was developed. This biprism is controlled similarly as a specimen holder so that it can be driven and rotated precisely and is tough against mechanical vibration and stray magnetic field. We recorded the maximum number of interference fringes by using this biprism in order to confirm the overall performance as a holography electron microscope, and obtained a world record of 11 000 interference fringes.
Combined optical and spatial modulation THz-spectroscopy for the analysis of thin-layered systems
Authors: Brucherseifer M. , Bolivar P. Haring , Kurz H.
Published: August 2002

We present a combined optical and spatial modulation technique to enhance drastically the resolution threshold of time-domain THz spectroscopy. By this approach, relative changes of THz transmission can be resolved down to unprecedented values of −90 dB, enabling the broadband analysis of extremely thin layered systems. The system capabilities are demonstrated by characterizing dielectric films, specifically a 1.2 μm thick polymer and a 100 nm thick SiO2 film.
In vacuo electron-spin-resonance study on amorphous fluorinated carbon films for understanding of surface chemical reactions in plasma etching
Authors: Ishikawa Kenji , Kobayashi Shoji , Okigawa Mitsuru , Sekine Makoto , Yamasaki Satoshi , Yasuda Tetsuji , Isoya Jun-ichi
Published: August 2002

An in vacuo electron-spin-resonance (ESR) technique was applied to study amorphous fluorinated carbon (a-C:F) films and their chemical reactivity with oxygen molecules. It was found that the carbon dangling bond (C-DB) density of an a-C:F film deposited at room temperature is as high as 2×1021 cm−3 and stable in vacuum. ESR spectra showed that there is a strong hyperfine interaction between the dangling bonds and the surrounding fluorine atoms. Experimental results indicate that an a-C:F film has a characteristic property that is suitable for SiO2 etching. Because a-C:F is highly reactive with oxygen, it can easily react with oxygen in underlying SiO2 to increase Si dangling bonds in SiO2.
Measurement of thermal-mechanical noise in microelectromechanical systems
Authors: Stievater T. H. , Rabinovich W. S. , Newman H. S. , Mahon R. , Goetz P. G. , Ebel J. L. , McGee D. J.
Published: August 2002

We report absolute measurements of thermal-mechanical noise in microelectromechanical systems. The devices are studied with an optical microcavity technique that has a resolution on the order of tens of femtometers per root hertz. The measured noise spectrum agrees with the calculated noise level to within 25%, a discrepancy most likely due to uncertainty in the effective dynamic mass of the vibrating bridge. These measurements demonstrate that thermal-mechanical noise can be the dominant noise source in actuated microelectromechanical devices.
Predicting water’s phase diagram and liquid-state anomalies
Authors: Truskett Thomas M. , Dill Ken A.
Published: August 2002

Water expands upon freezing, has minima in its volume, heat capacity, and isothermal compressibility with temperature, and shows signs of a first-order phase transition when supercooled. We present an analytical molecular theory that can account for these behaviors. It suggests that local network formation and hydrogen-bonding cooperativity between triplets of neighboring molecules are keys to understanding water’s thermodynamics.
Dramatically enhanced effective electrostriction in ferroelectric polymeric composites
Authors: Li JiangYu , Rao Nagadip
Published: August 2002

This letter reports a ferroelectric polymeric composite concept with dramatically enhanced effective electrostriction, strain energy density, and electromechanical coupling factor, where high-dielectric-constant ceramics are arranged in series with ferroelectric polymers having large electrostrictive strain. We demonstrate the importance of the dielectric constant of the constituent phases and the microstructural geometry of the composite on the effective electrostriction of the material.
Gas-phase production of monodisperse lead zirconate titanate nanoparticles
Authors: Seol Kwang Soo , Tomita Satoshi , Takeuchi Kazuo , Miyagawa Takeshi , Katagiri Takahiro , Ohki Yoshimichi
Published: August 2002

Laser ablative technology was used to prepare monodisperse nanoparticles (4–20 nm in diameter) of lead zirconate titanate (PZT). Laser ablation of a PZT ceramic target in oxygen ambience produced amorphous and irregularly shaped PZT nanoparticles. A subsequent on-line thermal treatment performed on the PZT nanoparticles dispersed in the gas phase brought about compaction and crystallization of the nanoparticles without additional particle growth. It was found that the amorphous nanoparticles began to crystallize above 600 °C, and they became a perovskite structure at 900 °C. The crystallized nanoparticles were then size classified by a differential mobility analyzer to yield monodisperse, highly pure, and single-crystalline PZT nanoparticles.
Spatial autocorrelation analysis of nanophotoluminescence images of single GaAs quantum wells
Authors: Neuberth U. , Walter L. , von Freymann G. , Schimmel Th. , Wegener M. , Khitrova G. , Gibbs H. M.
Published: August 2002

Introducing spatial autocorrelation analysis of nanophotoluminescence images of atomically rough single GaAs quantum wells, we show that the bright spots in the images are not randomly distributed but rather tend to “repel each other” along certain directions. Simple computer simulations on the anisotropic transport of excitons in the disorder potential and on the resulting images can reproduce this surprising behavior.
Three-dimensional integrated resonant tunneling transistor with multiple peaks
Authors: Lind Erik , Pietzonka Ines , Lindström Peter , Seifert Werner , Wernersson Lars-Erik
Published: August 2002

A resonant tunneling transistor was manufactured by integrating a self-aligned metallic gate 30 nm above and 100 nm below resonant tunneling diodes. The Schottky depletion around the gate controls the current to a confined vertical channel with a conduction area in the range of 100×100 nm. Due to the three-dimensional asymmetric placement of the gate with respect to the tunneling diodes, modulation of both the peak voltage and peak current was achieved.
Orientation-sensitive magnetic force microscopy for future probe storage applications
Authors: Litvinov Dmitri , Khizroev Sakhrat
Published: August 2002

A focused ion beam process was utilized to physically define a “point dipole” magnetic force microscopy (MFM) tip with cylindrical dimensions as small as 50 nm in diameter and 10 nm in height. By controlling the preferred orientation of the magnetization, it is possible to define directional sensitivity. The preferred orientation is controlled either by choosing a proper magnetic material with preferred crystalline anisotropy or by applying a sufficiently strong external magnetic field. The signal selectivity with respect to the imaged field orientation allows more direct information to be obtained from the imaged object, as compared to the information obtained from the same object when using a conventional MFM tip.
Low-temperature breakdown properties of AlxGa1−xAs avalanche photodiodes
Authors: Ma Feng , Karve Gauri , Zheng Xiaoguang , Sun Xiaoguang , Holmes Archie L. , Campbell Joe C.
Published: August 2002

Al x Ga 1−x As  (x=0.0–0.9) homojunction avalanche photodiodes are characterized in the temperature range of 11–300 K. For all compositions, the breakdown electric field strength decreases with temperature, and the rate of change is smaller at temperatures below 50 K than at higher temperatures. This results from the fact that spontaneous phonon emission dominates carrier scattering in the 0 K limit. The rate of change of the breakdown field strength is smallest for Al0.6Ga0.4As compared with other compositions. This is likely due to higher alloy scattering at x=0.6. A Monte Carlo model that provides good fits to experimental data is presented.
Experimental demonstration of oxide-mode influence in a dual-purpose oxide-confined vertical-cavity surface-emitting laser/resonant detector
Authors: Bardinal V. , Averseng L. , Bringer C. , Camps T. , Polesel-Maris J. , Dubreuil P. , Fontaine C. , Bedel-Pereira E. , Vergnenegre C. , Muñoz-Yagüe A.
Published: August 2002

We report on design, fabrication, and characterization of a vertical-cavity surface-emitting laser (VCSEL) used as a resonant-cavity-enhanced detector for dual-purpose application. The geometry of this oxide-confined VCSEL takes advantage of the properties of the buried oxide layer to allow both single-mode laser emission and detection on a large surface. Here, we demonstrate the presence and the influence of oxide modes in the optical sensitivity spectrum of the device through spatially localized detection measurements. The wavelength of these modes has been correlated to the dip on the reflectivity spectrum measured at the same area of the device surface.
Amorphous magnetic wires for medical locator applications
Authors: von Gutfeld R. J. , Dicello J. F. , McAllister S. J. , Ziegler J. F.
Published: August 2002

This letter evaluates the feasibility for implanting short segments of Barkhausen wires in treatment volumes of patients requiring radiation therapy. Such locating of deep-seated sites prior to each treatment is not done routinely or is usually achieved through imaging with ionizing radiations. Present therapeutic procedures can result in substantial heterogeneities in the dose distributions or significant doses to surrounding normal tissues, resulting in poorer control of the tumors and/or increased complications. The implants make it possible to accurately locate the wire by way of re-entrant flux measurements, and hence, pinpoint the treatment volume prior to and during treatment.
Two-dimensional optics with surface plasmon polaritons
Authors: Ditlbacher H. , Krenn J. R. , Schider G. , Leitner A. , Aussenegg F. R.
Published: August 2002

We report the experimental realization of highly efficient optical elements built up from metal nanostructures to manipulate surface plasmon polaritons propagating along a silver/polymer interface. Mirrors, beamsplitters, and interferometers produced by electron-beam lithography are investigated. The plasmon fields are imaged by detecting the fluorescence of molecules dispersed in the polymer.
Stability of a chemically bound helium compound in high-pressure solid helium
Authors: Bihary Z. , Chaban G. M. , Gerber R. B.
Published: August 2002

HHeF, a chemically-bound helium compound, has been predicted to be metastable in the gas phase. It decays by tunneling through energy barriers in picosecond timescales into He+HF and H+He+F. This paper studies the stability of HHeF in pressurized solid helium. Using realistic potentials for the HHeF/He interaction, the potential energy along the minimum energy paths for decomposition is evaluated, and tunneling decay times are computed by the WKB approximation. It is found that for pressures above 500 MPa, decomposition into H+He+F is completely suppressed. At 23 GPa, the highest pressure studied, the timescale for HHeF→He+HF is in the millisecond range. At pressures well above 23 GPa, HHeF is thus expected to remain stable indefinitely.
Ferromagnetism in cobalt–iron alloy nanowire arrays on W(110)
Authors: Pierce J. P. , Plummer E. W. , Shen J.
Published: August 2002

We have prepared arrays of parallel Fe1−xCox alloy nanowires along the atomic step edges of a miscut W(110) surface. Their magnetic properties have been studied with the surface magneto-optical Kerr effect as a function of the relative concentration of the two materials. At low (<35%) cobalt concentrations, the wire arrays exhibit a ferromagnetic easy axis along the substrate [1 −1 0] direction, which is in the surface plane, but perpendicular to the wires. Unlike the bulk alloy, this system shows a decrease in its Curie temperature as cobalt is added to pure Fe. The Curie temperature drops sharply near x=0.35, indicating that cobalt frustrates magnetic ordering in the system.
Optical and magnetic measurements of p-type GaN epilayers implanted with Mn+ ions
Authors: Shon Yoon , Kwon Young Hae , Yuldashev Sh. U. , Leem J. H. , Park C. S. , Fu D. J. , Kim H. J. , Kang T. W. , Fan X. J.
Published: August 2002

The p-type GaN epilayers were prepared by metalorganic chemical vapor deposition and subsequently Mn+ ions implanted. The properties of Mn+ ions-implanted GaN epilayers were investigated by optical and magnetic measurements. The results of photoluminescence measurement show that optical transitions related to Mn apparently appear at 2.5 eV and around 3.0 eV. It is confirmed that the photoluminescence peak at 2.5 eV is a donor–Mn acceptor transition. Ferromagnetic hysteresis loop was observed, and the temperature-dependent magnetization displayed a ferromagnetic behavior persisting up to ∼270 K.
Leveling and rebuilding: An approach to improve the uniformity of (In,Ga)As quantum dots
Authors: Gong Q. , Nötzel R. , Hamhuis G. J. , Eijkemans T. J. , Wolter J. H.
Published: August 2002

We report on an approach to improve the uniformity of a single layer of (In,Ga)As quantum dots (QDs) grown by molecular-beam epitaxy. The key concept of our approach is to level and rebuild the (In,Ga)As QDs during insertion of a short period GaAs/InAs superlattice between the (In,Ga)As QD layer and the GaAs capping layer. For optimized layer thickness and number of superlattice periods this process results in uniform (In,Ga)As QDs with narrow photoluminescence line width of 20 meV at 4.5 K.
Measurement of thermal conductivity of buried oxides of silicon-on-insulator wafers fabricated by separation by implantation of oxygen technology
Authors: He Ping , Liu Litian , Tian Lilin , Li Zhijian
Published: August 2002

In this work, an improved method for measuring the thermal conductivity of buried oxides of a silicon-on-insulator (SOI) wafer is proposed which is simple and effective. Using this method, the thermal conductivity of thin buried oxides with different SOI wafer thicknesses fabricated by separation by implantation of oxygen (SIMOX) technology is measured. It is found that at least in the range of thickness not less than 55 nm, the classically defined thermal conductivity of the SIMOX oxide remains constant (i.e., no size effect is observed) and is equal to 1.06 W m−1 K−1, which is smaller than the 1.4 W m−1 K−1 normally used value in device engineering. The boundary thermal resistance between the Si/SiO2 interface for SIMOX technology is measured accurately here. The results show that this boundary resistance cannot be neglected in calculation of the thermal resistance of SOI devices especially in the case of thinner back oxide.
AGGREGATE PRICE SHOCKS AND FINANCIAL INSTABILITY: A HISTORICAL ANALYSIS
Authors: Bordo Michael D. , Dueker Michael J. , Wheelock David C.
Published: September 2002

This article presents evidence on the relationship between price and financial stability. We construct an annual index of financial conditions for the United States, 1790–1997, and estimate the effect of aggregate price shocks on the index using a dynamic ordered probit model. We find that price‐level shocks contributed to financial instability during 1790–1933 and that inflation rate shocks contributed to financial instability during 1980–97. The size of the aggregate price shock needed to alter financial conditions depends on the institutional environment, but we conclude that a monetary policy focused on price stability would contribute to financial stability.
TOOLS OR TOYS? THE IMPACT OF HIGH TECHNOLOGY ON SCHOLARLY PRODUCTIVITY
Authors: Hamermesh Daniel S. , Oster Sharon M.
Published: September 2002

We examine the impact of communication technology on scholarly productivity by considering patterns of coauthored economics articles. Using articles in three major economics journals from 1970–79 and 1992–96, we find (1) sharp growth from distant coauthorships (authors not in the same metropolitan area prior to publication), as the theory predicts, and, contrary to theory, (2) lower productivity of distant than close‐coauthored works and no decline in their relative disadvantage. These findings are reconciled by noting that high technology has aspects of a consumer good. The relative productivity of solo‐authored articles has decreased, perhaps explaining the secular increase in coauthorship.
SIMILARITY JUDGMENTS AND ANOMALIES IN INTERTEMPORAL CHOICE
Authors: Leland Jonathan W.
Published: September 2002

This article demonstrates that choices based on similarity judgments will exhibit not only common ratio and reflection effects under uncertainty but also common difference and reflection effects in intertemporal contexts.
REPUTATIONAL COMPARATIVE ADVANTAGE AND MULTINATIONAL ENTERPRISE
Authors: Chisik Richard
Published: September 2002

For a firm without a readily identifiable brand name, quality reputation may solely reflect the country of origin. In this article I endogenize these country‐of‐origin reputations and show that these self‐fulfilling reputations determine not only the average quality of a country's exports but also the type of products in which a country specializes. Hence, the pattern of international trade can be determined by reputational comparative advantage. This specialization can also establish the location of the host and the parent firm in a multinational enterprise. Furthermore, this reputation effect can identify whether internalization or licensing is more likely to occur.
INDUSTRIAL RESPONSE TO ELECTRICITY REAL‐TIME PRICES: SHORT RUN AND LONG RUN
Authors: Schwarz Peter M. , Taylor Thomas N. , Birmingham Matthew , Dardan Shana L.
Published: September 2002

Real‐time pricing reduces summer peak demand by approximately 8% for 110 Duke Energy industrial customers. With up to six summers on the rate, the aggregate customer response increases with experience. Examining individual customers, only a subset respond significantly, primarily those who can self‐generate or with discrete (batch) production processes. These customers respond significantly above a threshold level of price. Although elasticities decrease slightly at the highest temperatures, the absolute quantity reductions are largest at these times.
BIDDING BEHAVIOR AND DECISION COSTS IN FIELD EXPERIMENTS
Authors: List John A. , Lucking‐Reiley David
Published: September 2002

Whether rationality of economic behavior increases with expected payoffs and decreases with the cognitive cost it takes to formulate an optimal strategy remains an open question. We explore these issues with field data, using individual bids from sealed‐bid auctions in which we sold nearly $10,000 worth of sports cards. Our results indicate that stakes do indeed matter, as high‐priced ($70) cards produced more of the theoretically predicted strategic behavior than did lower‐priced ($3) cards. We find additional evidence consistent with the importance of cognitive costs, as subjects more experienced with sports card auctions exhibited a greater tendency to behave strategically than did less experienced bidders.
USING BASEBALL CARD PRICES TO MEASURE STAR QUALITY AND MONOPSONY
Authors: Mullin Charles J. , Dunn Lucia F.
Published: September 2002

Baseball card prices are used to capture star quality in a new measure of productivity in Major League Baseball. Star quality, which impacts revenues, is determined from a player's baseball card price as the residual in a fit of card prices to performance statistics. This measure is entered into the computation of individual player marginal revenue product and compared to players' salaries using data from the four years leading up to the 1994 MLB strike. Results are examined for monopsonistic exploitation by market size, free agency status, type of player, and other relevant categories. Underpaid and overpaid players are identified.
DO CIVIL AND POLITICAL REPRESSION REALLY BOOST FOREIGN DIRECT INVESTMENTS?
Authors: Harms Philipp , Ursprung Heinrich W.
Published: September 2002

Multinational enterprises are often accused of having a preference for investing in countries in which the working populations' civil and political rights are largely disregarded. This article presents an empirical investigation of the popular “political repression boosts FDI” hypothesis and arrives at the conclusion that the hypothesis is not supported. On the contrary, multinational enterprises rather appear to be attracted by countries in which civil and political freedom is respected.
DO NATURAL DISASTERS PROMOTE LONG‐RUN GROWTH?
Authors: Skidmore Mark , Toya Hideki
Published: September 2002

In this article, we investigate the long‐run relationships among disasters, capital accumulation, total factor productivity, and economic growth. The cross‐country empirical analysis demonstrates that higher frequencies of climatic disasters are correlated with higher rates of human capital accumulation, increases in total factor productivity, and economic growth. Though disaster risk reduces the expected rate of return to physical capital, risk also serves to increase the relative return to human capital. Thus, physical capital investment may fall, but there is also a substitution toward human capital investment. Disasters also provide the impetus to update the capital stock and adopt new technologies, leading to improvements in total factor productivity.
Transcriptome analysis of
Escherichia coli
using high-density oligonucleotide probe arrays
Authors: Tjaden Brian , Saxena Rini Mukherjee , Stolyar Sergey , Haynor David R. , Kolker Eugene , Rosenow Carsten
Published: August 2002

Microarrays traditionally have been used to analyze the expression behavior of large numbers of coding transcripts. Here we present a comprehensive approach for high-throughput transcript discovery in Escherichia coli focused mainly on intergenic regions which, together with analysis of coding transcripts, provides us with a more complete insight into the organism’s transcriptome. Using a whole genome array, we detected expression for 4052 coding transcripts and identified 1102 additional transcripts in the intergenic regions of the E.coli genome. Further classification reveals 317 novel transcripts with unknown function. Our results show that, despite sophisticated approaches to genome annotation, many cellular transcripts remain unidentified. Through the experimental identification of all RNAs expressed under a specific condition, we gain a more thorough understanding of all cellular processes.
Role of transglutaminase 2 in glucose tolerance: knockout mice studies and a putative mutation in a MODY patient
Authors: BERNASSOLA FRANCESCA , FEDERICI MASSIMO , CORAZZARI MARCO , TERRINONI ALESSANDRO , HRIBAL MARTA L. , DE LAURENZI VINCENZO , RANALLI MARCO , MASSA ORNELLA , SESTI GIORGIO , MCLEAN W.H. IRWIN , CITRO GENNARO , BARBETTI FABRIZIO , MELINO GERRY
Published: August 2002

Transglutaminase 2 (TGase 2) is a Ca+2‐ dependent enzyme that catalyzes both intracellular and extracellular cross‐linking reactions by transamidation of specific glutamine residues. TGase 2 is known to be involved in the membrane‐mediated events required for glucose‐stimulated insulin release from the pancreatic β cells. Here we show that targeted disruption of TGase 2 impairs glucose‐stimulated insulin secretion. TGase 2‐/‐mice show glucose intolerance after intraperitoneal glucose loading. TGase 2‐/‐mice manifest a tendency to develop hypoglycemia after administration of exogenous insulin as a consequence of enhanced insulin receptor substrate 2 (IRS‐2) phosphorylation. We suggest that the increased peripheral sensitivity to insulin partially compensates for the defective secretion in this animal model. TGase 2‐/‐mouse phenotype resembles that of the maturity‐onset diabetes of young (MODY) patients. In the course of screening for human TGase 2 gene in Italian subjects with the clinical features of MODY, we detected a missense mutation (N333S) in the active site of the enzyme. Collectively, these results identify TGase 2 as a potential candidate gene in type 2 diabetes.—Bernassola, F., Federici, M., Corazzari, M., Terrinoni, A., Hribal, M. L., De Laurenzi, V., Ranalli, M., Massa, O., Sesti, G., Mclean, W. H. I., Citro, G., Barbetti, F., Melino, G. Role of transglutaminase 2 in glucose tolerance: knockout mice studies and a putative mutation in a MODY patient. FASEB J. 16, 1371–1378 (2002)
cDNA array analysis of gene expression profiles in the striata of wild‐type and Cu/Zn superoxide dismutase transgenic mice treated with neurotoxic doses of amphetamine
Authors: KRASNOVA IRINA N. , MCCOY MICHAEL T. , LADENHEIM BRUCE , CADET JEAN LUD
Published: August 2002

Amphetamine (AMPH) is a drug of abuse that causes the degeneration of striatal dopamine terminals in mammals. Superoxide radicals seem to participate in AMPH‐induced damage because its toxicity is attenuated in Cu/Zn superoxide dismutase transgenic (SOD‐tg) mice. To provide a detailed analysis of molecular changes associated with AMPH toxicity, we used cDNA arrays consisting of 1176 genes to detect differential changes in gene expression in the striata of wild‐type and SOD‐tg mice treated with neurotoxic doses of the drug. We found 42 genes that showed >1.8‐fold changes in at least two consecutive time points during the course of the study and were differentially affected by AMPH in the two genotypes. Specifically, more transcription factors and genes involved in responses to injury/inflammation were affected in wild‐type mice after AMPH administration. Some of these stimulant‐induced superoxide‐dependent alterations in gene expression might affect neuronal functions and promote neuronal damage. Other changes might help to provide some degree of protection against AMPH toxicity. These results support the view that the use of global array analysis of gene expression will help to identify novel molecular mediators of AMPH‐induced neurodegeneration.—Krasnova, I. N., McCoy, M. T., Ladenheim, B., Cadet, J. L. cDNA array analysis of gene expression profiles in the striata of wild‐type and Cu/Zn superoxide dismutase (SOD) transgenic mice treated with neurotoxic doses of amphetamine. FASEB J. 16, 1379–1388 (2002)
Development of hepatocytes from embryonic stem cells after transfection with the HNF‐3β gene
Authors: Ishizaka Shigeaki , Shiroi Akira , Kanda Seiji , Yoshikawa Masahide , Tsujinoue Hirohisa , Kuriyama Shigeki , Hasuma Tadayoshi , Nakatani Kazuki , Takahashi Kenichi
Published: August 2002

We have attempted to generate embryonic stem (ES) cell‐derived hepatocytes expressing liver‐specific functional properties by use of ES cell technology. It was found that ES cells are allowed to differentiate into hepatocytes possessing high metabolic activities when hepatocyte nuclear factor (HNF)‐3β‐transfected ES cells are cultured in α‐MEM medium supplemented with 10% fetal bovine serum (FBS) and fibroblast growth factor (FGF)‐2 in the three‐dimensional cell culture system at 5% CO2. The differentiated cells induced albumin, triacylglycerol, urea, and glycogen synthesis as well as further expression of metabolic proteins and serum factors as markers of hepatocytic differentiation for at least 4 months. The cells differentiated from HNF‐3β‐transfected ES cells also had hepatocyte‐like ultrastructural characteristics, including several endoplasmic reticula, mitochondrion, and glycogen. Our findings indicate that generation of hepatocytes maintaining high metabolic functions developed from mouse ES cells will facilitate the study of the basic mechanism for hepatogenesis and will certainly provide new opportunities for tissue transplantation.
Persistence of microscopic human cancers in mice: alterations in the angiogenic balance accompanies loss of tumor dormancy
Authors: UDAGAWA TATURO , FERNANDEZ ANTONIO , ACHILLES EIKE‐GERT , FOLKMAN JUDAH , D'AMATO ROBERT J.
Published: August 2002

Some human tumor lines do not form visible tumors when inoculated into immunosuppressed mice. The fate of these human tumor lines was followed by transfecting them with green fluorescence protein before inoculating them into mice. Although the tumor lines failed to grow progressively, they formed small dormant microscopic foci maintained at constant mass by balanced proliferation and apoptosis. Transfecting the cells with either VEGF165 or activated c‐Ha‐ras induced loss of dormancy, which correlated with a shift in the angiogenic balance toward increased vascularity with reduced tumor cell apoptosis. These results support a model in which loss of dormancy is controlled in part by a switch to an angiogenic phenotype. These tumor lines may serve as models for investigating the cellular mechanisms controlling dormancy and identifying those factors that promote the loss of balanced proliferation and apoptosis. Finally, these models may prove useful in the design and testing of therapies directed toward eradicating dormant tumors and preventing tumor recurrence.—Udagawa, T., Fernandez, A., Achilles, E.‐G., Folkman, J., D'Amato, R. J. Persistence of microscopic human cancers in mice: alterations in the angiogenic balance accompanies loss of tumor dormancy. FASEB J. 16, 1361–1370 (2002)
NMDA sensitization and stimulation by peroxynitrite, nitric oxide, and organic solvents as the mechanism of chemical sensitivity in multiple chemical sensitivity
Authors: PALL MARTIN L.
Published: August 2002

Multiple chemical sensitivity (MCS) is a condition where previous exposure to hydrophobic organic solvents or pesticides appears to render people hypersensitive to a wide range of chemicals, including organic solvents. The hypersensitivity is often exquisite, with MCS individuals showing sensitivity that appears to be at least two orders of magnitude greater than that of normal individuals. This paper presents a plausible set of interacting mechanisms to explain such heightened sensitivity. It is based on two earlier theories of MCS: the elevated nitric oxide/peroxynitrite theory and the neural sensitization theory. It is also based on evidence implicating excessive NMDA activity in MCS. Four sensitization mechanisms are proposed to act synergistically, each based on known physiological mechanisms: Nitric oxide‐mediated stimulation of neurotransmitter (glutamate) release; peroxynitrite‐mediated ATP depletion and consequent hypersensitivity of NMDA receptors; peroxynitrite‐mediated increased permeability of the blood–brain barrier, producing increased accessibility of organic chemicals to the central nervous system; and nitric oxide inhibition of cytochrome P450 metabolism. Evidence for each of these mechanisms, which may also be involved in Parkinson's disease, is reviewed. These interacting mechanisms provide explanations for diverse aspects of MCS and a framework for hypothesis‐driven MCS research.—Pall, M. L. NMDA sensitization and stimulation by peroxynitrite, nitric oxide, and organic solvents as the mechanism of chemical sensitivity in multiple chemical sensitivity. FASEB J. 16, 1407–1417 (2002)
In vivo gene transfer of soluble TNF‐α receptor 1 alleviates myocardial infarction
Authors: Sugano Masahiro , Koyanagi Masamichi , Tsuchida Keiko , Hata Tomoji , Makino Naoki
Published: August 2002

Apoptosis is the major independent form of cardiomyocyte cell death in acute myocardial infarction (AMI). TNF‐α release early in the course of AMI contributes to myocardial injury, and TNF‐α induces apoptosis in cardiomyocytes. Soluble TNF‐alpha receptor 1 (sTNFR1) is an antagonist to TNF‐α. However, the effect of sTNFR1 on AMI remains unclear. Here we report that direct injection of an sTNFR1 expression plasmid DNA to the myocardium reduces infarct size in experimental rat AMI. Treatment with sTNFR1 expression plasmid DNA reduced the TNF‐α bioactivity in the myocardium and the apoptosis of cardiomyocytes. These findings suggest that the anti‐TNF‐α therapy by sTNFR1 can be a new strategy for treatment of AMI.
Extracellular signal‐regulated kinases phosphorylate 5lipoxygenase and stimulate 5‐lipoxygenase product formation in leukocytes
Authors: Werz Oliver , Bürkert Eva , Fischer Lutz , Szellas Dagmar , Dishart David , Samuelsson Bengt , Rådmark Olof , Steinhilber Dieter
Published: August 2002

5‐Lipoxygenase (5‐LO) is the key enzyme in the biosynthesis of proinflammatory leukotrienes. Here, we demonstrate that extracellular signal‐regulated kinases (ERKs) can phosphorylate 5‐LO in vitro. Efficient phosphorylation required the presence of unsaturated fatty acids and was abolished when Ser‐663 was mutated to alanine. In intact HeLa cells stimulated with arachidonic acid (AA), impaired 5‐LO product formation was evident in cells expressing the S663A‐5‐LO mutant compared with cells expressing wild‐type 5‐LO. For Mono Mac 6 cells, priming with phorbol myristate acetate (PMA) before stimulation with ionophore was required for ERK1/2 activation and efficient 5‐LO phosphorylation, in parallel with substantial AA release and 5‐LO product formation. Inhibition of PKC by GF109203x or MEK1/2 by U0126 (or PD98059) abolished the 5‐LO up‐regulation effects of PMA. In contrast, these inhibitors failed to suppress 5‐LO product formation induced by stimuli such as AA plus ionophore, which apparently do not involve the ERK1/2 pathway. Based on inhibitor studies, ERKs are also involved in AA‐stimulated 5‐LO product formation in PMNL, whereas a role for ERKs is not apparent in 5‐LO activation induced by ionophore or cell stress. Finally, the data suggest that ERKs and p38 MAPK‐regulated MAPKAPKs can act in conjunction to stimulate 5‐LO by phosphorylation.
Human TNF‐α in transgenic mice induces differential changes in redox status and glutathione‐regulating enzymes
Authors: Glosli Heidi , Tronstad Karl Johan , Wergedal Hege , Müller Fredrik , Svardal Asbjørn , Aukrust Pål , Berge Rolf Kristian , Prydz Hans
Published: August 2002

Tumor necrosis factor α (TNF‐α) is a pleiotropic cytokine involved in several diseases. Various effects of TNF‐α are mediated by the induction of a cellular state consistent with oxidative stress. Glutathione (GSH) is a major redox‐buffer of eukaryotic cells and is important in the defense against oxidative stress. We hypothesized that persistent TNF‐α secretion could induce oxidative stress through modulation of GSH metabolism. This hypothesis was examined in a transgenic mouse model with low, persistent expression of human TNF‐α in the T cell compartment. Major findings were i) marked tissue‐specific changes in GSH redox status and GSH regulating enzymes, with the most pronounced changes in liver; ii) moderate changes in GSH metabolism and up‐regulation of GSH‐regulating enzymes were observed in lung and kidney from transgenic mice; and iii) liver, lung and kidney from transgenic mice had decreased levels of total glutathione, whereas splenic CD4+ and CD8+ T cells had a marked increase in oxidized glutathione as the major change.

Oxidative stress induced by persistent low‐grade exposure to TNF‐α in transgenic mice appears to involve marked organ‐specific alterations in glutathione redox status and glutathioneregulating enzymes with the most pronounced changes in the liver. These mice constitute a useful model for immunodeficiency syndromes and chronic inflammatory diseases involving pathogenic interaction between TNF‐α and oxidative stress.
Androgen receptor with elongated polyglutamine tract forms aggregates that alter axonal trafficking and mitochondrial distribution in motoneuronal processes
Authors: Piccioni Federica , Pinton Paolo , Simeoni Silvia , Pozzi Paola , Fascio Umberto , Vismara Guglielmo , Martini Luciano , Rizzuto Rosario , Poletti Angelo
Published: August 2002

The CAG/polyglutamine (polyGln)‐related diseases include nine different members that together form the most common class of inherited neurodegenerative disorders; neurodegeneration is linked to the same type of mutation, found in unrelated genes, consisting of an abnormal expansion of a polyGln tract normally present in the wild‐type proteins. Nuclear, cytoplasmic, or neuropil aggregates are detectable in CAG/polyGln‐related diseases, but their role is still debated. Alteration of the androgen receptor (AR), one of these proteins, has been linked to spinal and bulbar muscular atrophy, an X‐linked recessive disease characterized by motoneuronal death. By using immortalized motoneuronal cells (the neuroblastoma‐spinal cord cell line NSC34), we analyzed neuropil aggregate formation and toxicity: green fluorescent protein‐tagged wild‐type or mutated ARs were cotransfected into NSC34 cells with a blue fluorescent protein tagged to mitochondria. Altered mitochondrial distribution was observed in neuronal processes containing aggregates; occasionally, neuropil aggregates and mitochondrial concentration corresponded to axonal swelling. Neuropil aggregates also impaired the distribution of the motor protein kinesin. These data suggest that neuropil aggregates may physically alter neurite transport and thus deprive neuronal processes of factors or components that are important for axonal and dendritic functions. The soma may then be affected, leading to neuronal dysfunctions and possibly to cell death.