bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental investigation for field-induced interaction force of two spheres
Authors: Wang Zhiyong , Peng Zheng , Lu Kunquan , Wen Weijia
Published: March 2003

An apparatus is developed to study the interaction forces between two spheres under an external ac electric field. The interaction forces of a pair of spheres as the function of interspherical spacing, electric field strength, and electric field frequency are measured precisely. The results reveal that much stronger interaction can be obtained for metal spheres and high-dielectric spheres compared with the spheres with a very low dielectric constant, such as glass and polymer. The measured forces increase very steeply as the gap of the spheres decreases, and become much larger than those of available theoretical predictions when the two single-crystalline spheres of SrTiO3 are closely spaced. The frequency dependence of the interaction force also shows an anomalous behavior. Our measurements indicate that a more accurate theoretical calculation should be performed to explain the experimental results.
Spectral and time-resolved photoluminescence studies of Eu-doped GaN
Authors: Nyein Ei Ei , Hömmerich U. , Heikenfeld J. , Lee D. S. , Steckl A. J. , Zavada J. M.
Published: March 2003

We report on spectral and time-resolved photoluminescence (PL) studies performed on Eu-doped GaN prepared by solid-source molecular-beam epitaxy. Using above-gap excitation, the integrated PL intensity of the main Eu3+ line at 622.3 nm (5D0→7F2 transition) decreased by nearly 90% between 14 K and room temperature. Using below-gap excitation, the integrated intensity of this line decreased by only ∼50% for the same temperature range. In addition, the Eu3+ PL spectrum and decay dynamics changed significantly compared to above-gap excitation. These results suggest the existence of different Eu3+ centers with distinct optical properties. Photoluminescence excitation measurements revealed resonant intra-4f absorption lines of Eu3+ ions, as well as a broad excitation band centered at ∼400 nm. This broad excitation band overlaps higher lying intra-4f Eu3+ energy levels, providing an efficient pathway for carrier-mediated excitation of Eu3+ ions in GaN.
Morphology and surface reconstructions of GaN(11̄00) surfaces
Authors: Lee C. D. , Feenstra R. M. , Northrup J. E. , Lymperakis L. , Neugebauer J.
Published: March 2003

GaN is grown by plasma-assisted molecular-beam epitaxy on ZnO(11̄00) substrates. Well-oriented (11̄00) GaN surfaces are obtained, and (11̄01) oriented facets are also observed. On the GaN(11̄00) surfaces under Ga-rich conditions, a surface reconstruction with approximate symmetry of “4×5” is found. A model is proposed in which this reconstruction consists of ⩾2 monolayers of Ga terminating the GaN surface.
High-selectivity etching of polycrystalline 3C-SiC films using HBr-based transformer coupled plasma
Authors: Gao Di , Howe Roger T. , Maboudian Roya
Published: March 2003

We report a highly selective reactive ion etching process for 3C-SiC films using HBr-based chemistry in a commercial transformer coupled plasma (TCP) etcher. SiO2 and Si3N4 are employed as etch masks. Etch rates for SiC, SiO2, and Si3N4 are measured as functions of chamber pressure and TCP source power. Etch rate ratios of 20:1 for SiC/SiO2 and 22:1 for SiC/Si3N4 are achieved. In addition, a SiC micromechanical resonator is fabricated to demonstrate integration of the etching process into conventional microfabrication technologies.
Step-edge kinetics driving the formation of atomically flat (110) GaAs surfaces
Authors: Oh Ji-Won , Yoshita Masahiro , Akiyama Hidefumi , Pfeiffer Loren N. , West Ken W.
Published: March 2003

Atomically flat (110) GaAs surfaces fabricated by the cleaved-edge overgrowth method and high-temperature growth-interrupt annealing are characterized at the atomic scale. We observe atomically flat (110) surfaces extending over areas more than 100 μm in size. Moreover, deposition of slightly less or more than integral monolayers (MLs) causes the appearance of characteristic step-edge shapes such as 1-ML-deep pits, or 2-to-3-ML-high isolated islands. Statistical analysis on the size and shape distribution of the 1-ML-deep pits supports a simple model based on the stability of Ga and As atoms on step edges with different bonding configurations, and reveals driving force to form an atomically flat (110) surface.
Fabrication of three-dimensional polymer photonic crystal structures using single diffraction element interference lithography
Authors: Divliansky Ivan , Mayer Theresa S. , Holliday Kito S. , Crespi Vincent H.
Published: March 2003

This letter describes an approach for recording three-dimensional (3D) periodic structures in a photosensitive polymer using a single diffraction element mask. The mask has a central opening surrounded by three diffraction gratings oriented 120° relative to one another such that the three first order diffracted beams and the nondiffracted laser beam give a 3D spatial light intensity pattern. Structures patterned in this polymer using 1.0 and 0.56 μm grating periods have hexagonal symmetry with micron- to submicron-periodicity over large substrate area. Band structure calculations of these low index contrast materials predict photonic gaps in certain high symmetry directions.
Point-dipole response from a magnetic force microscopy tip with a synthetic antiferromagnetic coating
Authors: Wu Yihong , Shen Yatao , Liu Zhiyong , Li Kebin , Qiu Jinjun
Published: March 2003

A point-dipole-like magnetic force microscopy tip has been realized using an antiferromagnetically coupled synthetic structure consisting of two CoCrPt layers separated by an ultrathin Ru layer. This is made possible through magnetizing one of the CoCrPt layers in either upward or downward direction along the tip axis and the other in the opposite direction through antiferromagnetic coupling. The new tip was found to have a superior resolution and a point-dipole-like magnetic response when being used to image magnetic patterns recorded on longitudinal media.
Electromechanical properties of Nd-doped Bi4Ti3O12 films: A candidate for lead-free thin-film piezoelectrics
Authors: Maiwa Hiroshi , Iizawa Naoya , Togawa Daichi , Hayashi Takashi , Sakamoto Wataru , Yamada Mio , Hirano Shin-ichi
Published: March 2003

Neodymium-doped Bi4Ti3O12 (BNT) films are evaluated for use as lead-free thin-film piezoelectrics in microelectromechanical systems. Bi4Ti3O12, Bi3.25La0.75Ti3O12, and Bi3.25Nd0.75Ti3O12 films were fabricated by chemical solution deposition on Pt/TiOx/SiO2/Si substrates. Nd substitution promoted random orientation with low (00l) diffraction peaks. The 1-μm-thick Bi3.25Nd0.75Ti3O12 film annealed at 750 °C exhibited a remanent polarization of 26 μC/cm2. Typical butterfly field-induced strain loops were obtained in the BNT film capacitors. The electrically induced strain is 8.4×10−4 under the bipolar driving field of 220 kV/cm. These results show that BNT is a promising candidate for use in lead-free thin-film piezoelectrics.
Field-effect transistors on rubrene single crystals with parylene gate insulator
Authors: Podzorov V. , Pudalov V. M. , Gershenson M. E.
Published: March 2003

We report on the fabrication and characterization of the organic field-effect transistors (OFETs) on the surface of single crystals of rubrene. The parylene polymer film has been used as the gate insulator. At room temperature, these OFETs exhibit the p-type conductivity with the field-effect mobility 0.1–1 cm2/V s and the on/off ratio⩾104. The temperature dependence of the mobility is discussed.
Void channel microstructures in resin solids as an efficient way to infrared photonic crystals
Authors: Ventura M. J. , Straub M. , Gu M.
Published: March 2003

Microvoid channels were generated by local melting in a solidified polymer resin sample moving perpendicular to the focus of a high numerical-aperture objective under visible femtosecond-pulsed illumination. Channel size, surface quality, and high density channel vicinity depended on laser intensity and scanning speed. Electron microscope images revealed elliptical channel cross sections of 0.7–1.3 μm in lateral diameter and an elongation in the focusing direction of approximately 50%. A 20 layer woodpile-type photonic crystal structure with a 1.7 μm layer spacing and a 1.8 μm in-plane channel spacing provided a sharp peak in reflection and a suppression of infrared transmission in the stacking direction by 85% at wavelength 4.8 μm with a gap/midgap ratio of 0.11.
Alloy states in dilute GaAs1−xNx alloys (x<1%)
Authors: Luo X. D. , Huang J. S. , Xu Z. Y. , Yang C. L. , Liu J. , Ge W. K. , Zhang Y. , Mascarenhas A. , Xin H. P. , Tu C. W.
Published: March 2003

A set of GaAs1−xNx samples with small nitrogen composition (x<1%) were investigated by continuous-wave photoluminescence (PL), pulse-wave excitation PL, and time-resolved PL. In the PL spectra, an extra transition located at the higher-energy side of the commonly reported N-related emissions was observed. By measuring the PL dependence on temperature and excitation power, the PL peak was identified as a transition of alloy band edge-related recombination in GaAsN. The PL dynamics further confirms its intrinsic nature as being associated with the band edge rather than N-related bound states.
Parametric study of Ga1−xInxNyAs1−y/GaAs quantum wells for 1.3-μm laser operation
Authors: Chow W. W. , Harris J. S.
Published: March 2003

A microscopic laser theory was used to investigate gain properties in Ga1−xInxNyAs1−y/GaAs quantum wells. We considered combinations of x and y giving laser emission around 1.30 μm. Optical properties affecting laser threshold and dynamical response are described for structures with strain ranging from compressive to tensile. A parametric study of this kind should provide useful information for the optimization of GaInNAs vertical-cavity surface-emitting laser gain media for telecommunications applications.
Exciton quenching in Pt/GaN Schottky diodes with Ga- and N-face polarity
Authors: Shokhovets S. , Fuhrmann D. , Goldhahn R. , Gobsch G. , Ambacher O. , Hermann M. , Karrer U. , Eickhoff M.
Published: March 2003

We observed a peculiar dependence of low-temperature electroreflectance spectra of Pt/GaN Schottky diodes with Ga- and N-face polarity on the bias voltage (so-called “rotation” spectra), indicating the quenching of discrete exciton states and the formation of an exciton dead layer (EDL) beneath the gate. Data analysis is carried out using the field-dependent dielectric function of GaN. It yields parameters of excitons for the zero-field limit and the depth of the EDL, as well as the surface band bending and the ionized impurity concentration.
Formation of regular arrays of silicon microspikes by femtosecond laser irradiation through a mask
Authors: Shen M. Y. , Crouch C. H. , Carey J. E. , Younkin R. , Mazur E. , Sheehy M. , Friend C. M.
Published: March 2003

We report fabrication of regular arrays of silicon microspikes by femtosecond laser irradiation of a silicon wafer covered with a periodic mask. Without a mask, microspikes form, but they are less ordered. We believe that the mask imposes order by diffracting the laser beam and providing boundary conditions for capillary waves in the laser-melted silicon.
Ordering self-assembled islands without substrate patterning
Authors: Capellini G. , De Seta M. , Spinella C. , Evangelisti F.
Published: March 2003

The self-patterning of the strain field that arises in the growth of stacked multilayers of heteroepitaxial islands, together with the capability of tuning the island size by acting on the deposition temperature, are here exploited to obtain self-organization, resulting in well-ordered clusters composed of regularly disposed, nanosized islands. Our results show that the island spatial distribution can be tuned from a random one to a well-ordered square lattice of island clusters, and that the number of islands inside each cluster can be selected. Moreover, due to the dipole repulsive interaction between adjacent islands, the islands themselves arrange in an ordered fashion inside a single cluster along the same [010]-[100] crystalline directions of the long-range cluster ordering.
Magnetic study of an amorphous conducting polyaniline
Authors: Chaudhuri Debangshu , Kumar Ashwani , Sarma D. D. , Garcı́a-Hernández M. , Joshi Janhavi P. , Bhat S. V.
Published: March 2003

We show that newly found BF3-doped polyaniline, although highly conducting, remains amorphous. Magnetic studies reveal many unusual properties, while suggesting that the intrinsic conductivity of this system is significantly larger than all other known forms of conducting polyaniline, establishing it as an interesting class of highly conducting amorphous polymer.
Control of spin functionality in ZnMnSe-based structures: Spin switching versus spin alignment
Authors: Buyanova I. A. , Rudko G. Yu. , Chen W. M. , Toropov A. A. , Sorokin S. V. , Ivanov S. V. , Kop’ev P. S.
Published: March 2003

The ability of attaining desired spin functionality by adjusting structural design is demonstrated in diluted magnetic semiconductor (DMS) quantum structures based on II–VI semiconductors. The following spin enabling functions are achieved by tuning the ratio between the rates of exciton spin relaxation within the DMS and exciton escape from it to an adjacent nonmagnetic spin detector. Spin switching is realized when using a thin layer of Zn0.95Mn0.05Se as a spin manipulator and is attributed to a fast exciton escape from the DMS preceding the spin relaxation. Spin alignment is accomplished in tunneling structures where the presence of an energy barrier inserted between a spin manipulator (a DMS-based superlattice) and a spin detector ensures a slow escape rate from the DMS layer.
Current-induced structural modification of silicon-on-insulator nanocircuits
Authors: Clement N. , Francinelli A. , Tonneau D. , Scotto Ph. , Jandard F. , Dallaporta H. , Safarov V. , Fraboulet D. , Gautier J.
Published: March 2003

Silicon-on-insulator (SOI) materials are considered the next form of Si for extending the metal–oxide–silicon technology. Here, we report the electrical study correlated with the topographical modification of nanostructures built on 20-nm-thick SOI. At current densities around 3×106 A cm−2, we noticed an irreversible modification characterized by formation of nanochannels and failures at n+n contacts. The origin of these channels can be attributed either to hydrodynamic diffusion of positive Si ions or to momentum exchange with holes created by impact ionization at high electric field (105 V/cm). We show also that the heating of the circuit plays an important role in the process.
Ni-seeding effects on the properties of polycrystalline silicon–germanium grown at low temperature
Authors: Zhang Jianjun , Shimizu Kousaku , Hanna Junichi
Published: March 2003

We have investigated the Ni-seeding effects on the low-temperature growth of the polycrystalline silicon–germanium (poly-SixGe1−x) films by reactive thermal chemical vapor deposition with Si2H6 and GeF4. Very thin Ni films (<2 nm) were deposited on the glass substrates by electron beam evaporation in prior to poly-SixGe1−x deposition. The crystallinity and electrical performance of the poly-SixGe1−x films were characterized. p-channel bottom-gate thin-film transistors (TFTs) were also fabricated with these films to evaluate the effect of Ni seeding on device performance. We found that a certain amount of Ni, i.e., less than 0.5 nm, impacts upon the grain size and crystallinity without additional degradation of electrical properties due to the incorporation of Ni in the film. A 0.2 nm equivalent thickness of Ni gives the best crystallinity and the largest grain size (135 nm) and results in the highest mobility (31 cm2/V s) in p-channel TFTs fabricated on SiO2/Si substrates.
Low-frequency noise overshoot in ultrathin gate oxide silicon-on-insulator metal–oxide–semiconductor field-effect transistors
Authors: Mercha A. , Simoen E. , van Meer H. , Claeys C.
Published: March 2003

A noise overshoot phenomenon occurring in the ohmic regime is described in fully depleted and partially depleted silicon-on-insulator metal–oxide–semiconductor field-effect transistors with 2.5 nm nitrided gate oxide. It is characterized by a peak in the current noise spectral density S1 versus the front gate voltage VGS, whereby the peak amplitude can be several orders of magnitude higher than the background 1/f noise. In addition, it is shown that the corresponding spectrum has a Lorentzian shape. Associated with this noise peak is a second maximum in the device transconductance. It is believed that the mechanism of this excess noise is similar as for the kink-related noise overshoot, found in saturation. However, the origin of this floating-body effect is believed to be related to electron valence-band tunneling through the thin dielectric and occurring for a sufficiently large gate voltage.
Structure and magnetic properties of high coercive NdFeB films with a perpendicular anisotropy
Authors: Serrona L. K. E. B. , Sugimura A. , Adachi N. , Okuda T. , Ohsato H. , Sakamoto I. , Nakanishi A. , Motokawa M. , Ping D. H. , Hono K.
Published: March 2003

Relatively good hard magnetic properties obtained from Nd2Fe14B films prepared by the rf sputtering technique were investigated in terms of the microstructural development. Although as-deposited films on Mo substrates deposited at substrate temperatures (Ts) of 365 °C were amorphous with the dispersion of nanocrystalline NdO particles, columnar grains of Nd2Fe14B phase with the c-axis perpendicular to the film plane developed after annealing at 650 °C at an optimized heating rate. Nd2Fe14B grain size was about 400 nm in average and NdO particles of about 10 nm were dispersed within the grains and along the grain boundaries. These films exhibited good perpendicular hard magnetic properties of Hci=1356 kA/m and (BH)MAX∼216 kJ/m3.
Infrared ellipsometry of GaAs epilayers on Si(100)
Authors: Yu G. , Rowell N. L. , Lockwood D. J. , Soga T.
Published: March 2003

Infrared spectroscopic ellipsometry is used to characterize the structure of molecular-beam-epitaxial grown GaAs layers on Si(100) before and after thermal cycle (TC) annealing. The dielectric function of the GaAs epilayer has been described by the sum of a factorized form and a classical Drude model in the spectral fitting procedure. The epilayer LO phonon frequency shifts toward lower frequency with increasing TC number while the opposite is seen for TO phonon. The shift of the LO mode indicates that the tensile stress increases with increasing TC number, while the shift of the TO mode is attributed mainly to the self-energy effect in GaAs:Si. Unequal thermal diffusion of SiAs− and SiGa+ is indicated.
Magnetotransport of p-type GaMnN assisted by highly conductive precipitates
Authors: Kim K. H. , Lee K. J. , Kim D. J. , Kim H. J. , Ihm Y. E. , Djayaprawira D. , Takahashi M. , Kim C. S. , Kim C. G. , Yoo S. H.
Published: March 2003

GaMnN growth on GaAs (100) using a GaN single precursor via molecular beam epitaxy was undertaken. The grown layers revealed p-type conduction. It is confirmed that p-GaMnN reveals room temperature ferromagnetism with hysteresis loop having a coercivity of ∼100 Oe. The segregated phase showing a transition temperature of ∼200 K is assigned to Mn3GaN, and which enhances the conductivity of the surrounding GaMnN region. As a consequence, the GaMnN layer with segregation revealed an anomalous Hall effect at room temperature proving magnetotransport in GaMnN phase. The enhanced conductivity of GaMnN by the highly conductive second phase also revealed the importance of the role of the free carriers in the carrier-mediated ferromagnetism.
Femtosecond laser-induced periodic surface structure on diamond film
Authors: Wu Qihong , Ma Yurong , Fang Rongchuan , Liao Yuan , Yu Qingxuan , Chen Xiangli , Wang Kelvin
Published: March 2003

We report the laser-induced periodic surface structure (LIPSS) with periodicity about a quarter of the laser wavelength on unpolished diamond film treated by a P-polarized femtosecond laser. The short period LIPSS is parallel to the laser polarization and independent on the incidence angle. The LIPSS perpendicular to the laser polarization with periodicity shorter than a third of the laser wavelength slightly dependent on the incidence angle is also observed as well as the LIPSS perpendicular to the laser polarization with periodicity dependent on the incidence angle. The results are explained by interference of the incident laser and surface scattered wave related to the excited electrons during laser interactions with diamond, being in excellent agreement with a previously developed theory.
Interferometric study of thermal dynamics in GaAs-based quantum-cascade lasers
Authors: Pflügl C. , Litzenberger M. , Schrenk W. , Pogany D. , Gornik E. , Strasser G.
Published: March 2003

The thermal dynamics in quantum-cascade lasers under pulsed operation is investigated by a scanning interferometric thermal mapping technique. An infrared laser beam probes the change in the refractive index caused by current-induced heating of the working devices. The measured phase shift provides a quantitative information on the thermal characteristics with a micrometer spatial and a nanosecond time resolution. Comparing the experiments with a two-dimensional thermal model enables us to determine the anisotropic heat conductivity in the multilayered active region, found to be much lower than the one of bulk GaAs, as well as the temperature increase in the active region during pulsed operation.
Three-dimensional orientation of single molecules observed by far- and near-field fluorescence microscopy
Authors: Vacha Martin , Kotani Masahiro
Published: March 2003

We present a simple and straightforward method for determining absolute spatial orientations of transition dipole moments of single fluorescent molecules. Far-field polarization microscopy provides angles of the dipole moments projected in the plane of the sample. Optical field near total internal reflection surfaces has a strong component perpendicular to the sample and, for a given in-plane angle, provides unambiguous orientation of the molecular dipole moment. Experimentally, both excitation modes are alternated to monitor real-time conformational dynamics of tetramethylrhodamine molecules covalently attached to a quartz substrate.
Fabrication of thiol-capped Pd nanoparticles: An electrochemical method
Authors: Zhang P. , Sham T. K.
Published: March 2003

A simple electrochemical method is developed to prepare thiol-capped Pd nanoparticles on a Si (100) surface by reducing Pd2+ in solution in the presence of thiol molecules. The structure, bonding, and electronic properties of the electrodeposited Pd nanoparticles (NPs), together with a series of Pd model systems, were studied by electron microscope and x-ray absorption spectroscopy at the S K-edge and the Pd L3,2-edge. The thiol-capped electrodeposits are found to be metallic Pd particles of a few nanometers, with local structures and electronic behavior considerably different from the non-thiol-capped electrodeposits, but rather comparable to colloidal thiol-capped NPs.
Large memory window and long charge-retention time in ultranarrow-channel silicon floating-dot memory
Authors: Saitoh Masumi , Nagata Eiji , Hiramoto Toshiro
Published: March 2003

We propose and demonstrate an ultranarrow-channel silicon floating-dot memory, in which the channel width is scaled to sub-10 nm. In the fabricated ultranarrow-channel memory, a larger threshold voltage shift has been observed than in the wide-channel memory. From numerical calculations, it turns out that this is caused by bottleneck regions that dominate the conductance of the whole channel in the ultranarrow-channel. Moreover, longer charge-retention time has been also obtained in the fabricated ultranarrow-channel memory. This can be explained by the nonlinear dependence of the threshold voltage shift on the number of electrons in the dots due to the classical bottleneck effect and the increase in the ground state energy of the channel due to the quantum confinement.
Mass and size effects on the memory function of tracer particles
Authors: Kneller G. R. , Hinsen K. , Sutmann G.
Published: March 2003

Using autoregressive modeling of discrete signals, we investigate the influence of mass and size on the memory function of a tracer particle immersed in a Lennard-Jones liquid. We find that the memory function of the tracer particle scales with the inverse reduced mass of the simulated system. Increasing the particle’s mass leads rapidly to a slow exponential decay of the velocity autocorrelation function, whereas the memory function changes just its amplitude. This effect is the more pronounced the smaller and the heavier the tracer particle is.
Public Housing and the Rescaling of Regulation in the USA
Authors: Hackworth Jason
Published: March 2003

The simultaneous upward and downward rescaling of regulation has dramatically altered welfare provisioning systems in very different national contexts during the past thirty years. Frequently lost in the literature on rescaling, though, is the notion that localities have not been ‘given’ power in the same way that international institutions have. Though local institutional variation accounts for more difference in welfare provision than before, there are clear policy boundaries that are policed by market regulators of various sorts. This paper explores the impact of rescaling on public housing provision in the United States to illustrate better this point. I demonstrate that basic demographic, housing stock, and federal funding differences are now less important determinants of uneven public housing production than was the case during the Keynesian era, and that local institutional differences are now playing a greater role in the production and management of public housing. With such institutional differences unleashed, enormous variation in the quantity, quality, and management of public housing is now emerging.
On Promising Niches and Constraining Sociotechnical Regimes: The Case of Dutch Wheat and Bread
Authors: Wiskerke Johannes S C
Published: March 2003

Growing concerns about the consequences of large scale production systems and, subsequently, the growing public demand for changing the dominant mode of agricultural production have become important issues on the European political agenda. In recent years the number of new or alternative food supply chains and networks that incorporate claims of sustainability and quality has grown impressively. However, compared to conventional food supply chains and networks these alternative chains and networks remain rather small. By using the example of Dutch wheat and bread, in this paper I demonstrate that the prevailing sociotechnical regime constrains the growth of new promising sustainable food supply chains and networks. Constraints are both of a technical and an institutional nature. Strategic niche management is proposed as a promising design tool to overcome some of the encountered constraints, with the aim of contributing to a transition towards a more sustainable sociotechnical regime.
Metabolising Risk: Food Scares and the Un/Re-Making of Belgian Beef
Authors: Stassart Pierre , Whatmore Sarah J
Published: March 2003

In this paper we explore the event of foodscares as an example of what Callon calls ‘hot situations’, in which the landscape of competing knowledge claims is at its most molten, and alternative production and consumption practices galvanise new modes of sense-making against the market and state-sanctioned rationalities of industrialisation. Through a case study of the Belgian cooperative Coprosain and its meat products, we examine the ‘stuff’ of food as a ready messenger of connectedness and affectivity in which ‘risk’ is transacted as a property both of the growing distance between the spaces of production and consumption and of the enduring metabolic intimacies between human and nonhuman bodies.
Contesting the State: Discourses of the Asian Economic Crisis and Mediating Strategies of Electronics Firms in Singapore
Authors: Lai Karen P Y , Yeung Henry Wai-chung
Published: March 2003

In the last decade or so, human geographers have paid greater attention to the significance of discourses. We acknowledge the importance of discursive constructions and metaphorical representations of economic space, and extend the argument by examining the practices that may follow from such discourses. With use of empirical data from a firm-level survey and interviews with representatives of electronics firms in Singapore, we focus on contested interpretations of the Asian economic crisis at the firm level: how they might differ from state-driven discourses, and the extent to which state discourses (embodied in ministerial speeches and policy initiatives) were accepted, contested, and negotiated through firm-specific practices. The different counterdiscourses and responses of local and foreign firms are also compared. Results show that discourses at the national (state) scale were challenged and contested by firms within the same national space economy because of such material conditions as firm-specific circumstances, spatial extensiveness of their intrafirm and interfirm networks, and their access to various formal and informal information channels. The sampled firms offerered their own readings of the crisis that often contradicted the effectiveness and usefulness of certain policy responses orchestrated at the national scale. Their abilities to weather the crisis were also differentiated significantly between local and foreign firms. The study therefore highlights the importance of understanding the complex interrelationships between discourses and practices at different spatial scales and their capacity to produce (un)intended geographical outcomes.
Automated Pricing Rules in Electronic Posted Offer Markets
Authors: Deck Cary A. , Wilson Bart J.
Published: March 2003

Internet markets are heralded as enhancing efficiency by providing buyers and sellers with an abundance of information. In these electronic markets, firms have the opportunity to employ “pricebots,” computerized algorithms that automatically adjust prices to prevailing market conditions. This article uses laboratory methods to examine the potential market impact of the endogenous selection of three automated pricing algorithms: undercutting, low‐price matching, and trigger pricing. We find that the undercutting algorithm leads to prices similar to the game‐theoretic prediction. Low‐price matching generates significantly higher prices, and trigger pricing results in market prices below the game‐theoretic prediction.
Democrats, Dictators, and Demonstrators
Authors: Minier Jenny A.
Published: March 2003

Using a data set of democratic movements and democratic transitions that took place between 1960 and 1990, I investigate the implications for economic growth of these events. There are two comparisons of interest: successful democratic movements to movements that are repressed, and successful democratic movements to democratic transitions that occurred without such movements. None of these events has a positive effect on economic growth.
Nominal and Real Disturbances and Money Demand in Chinese Hyperinflation
Authors: Tallman Ellis W. , Tang De‐Piao , Wang Ping
Published: March 2003

This article reexamines the dynamics of hyperinflation by allowing variability in the relative price of capital goods in units of consumption goods that reflects interactions between the real and monetary sectors. The theory generates empirically testable implications that suggest expanding the standard Caganian money demand function to include both anticipated inflation and relative price effects in a nonlinear fashion. Employing data from the post–WW II Chinese hyperinflationary episode, the empirical findings suggest that conventional econometric investigations of money demand during hyperinflation overlook important nonlinear interactions between real and monetary activities and, hence, underestimate the welfare costs of hyperinflation.
An Empirical Examination of Quality Certification in a “Lemons Market”
Authors: Wimmer Bradley S. , Chezum Brian
Published: March 2003

This article examines the effect third‐party certification has on a market characterized by adverse selection. Using an original data set from the market for young thoroughbreds, we show that certification alleviates problems of adverse selection by examining the effect certification has on breeder decisions to retain or sell horses and the effect these decisions have on observed prices. Data on the racetrack performance of the horses confirm the results.
On the Third Law of Demand
Authors: Razzolini Laura , II Shughart William F. , Tollison Robert D.
Published: March 2003

The Alchian and Allen theorem predicts that it will be harder to find “good” apples in the State of Washington, a prime apple‐growing region, than in, say, New York City, where the addition of shipping charges makes “bad” apples comparatively more expensive. We recast the theorem as a testable proposition by explicitly taking the supply side into account and identifying plausible scenarios in which a fixed cost either has no effect on the relative prices of high and low quality grades of the same good in distant markets or, indeed, causes more of the bad apples to be shipped out.
Optimality of Investment under Imperfectly Enforceable Financial Contracts
Authors: Chu Hsiao‐Lei , Chen Nan‐Kuang
Published: March 2003

We investigate the optimality of aggregate investment and its policy implications under an environment in which financial contracts are imperfectly enforceable. We show that too much investment occurs when the ratio of own capital to debt is smaller than the ratio of project returns in terms of future values across periods, and too low investment occurs otherwise. A subsidy (tax) on the risk‐free interest income can close the over‐ (under‐) investment gap, but this policy may not be welfare improving.
The Effects of Congressional Appropriation Committee Membership on the Distribution of Federal Research Funding to Universities
Authors: Payne A. Abigail
Published: March 2003

Does congressional representation of a university affect the distribution of research funding to universities? This article studies two types of congressional representation: district representation, reflecting interests related to the politician's constituents, and alma mater affiliation, reflecting the politician's personal interests. I find that both types of representation matter and lobbying efforts by public and private universities may differ. Thus this article suggests politics plays a role in diverting funding that might be given to other institutions based under a more objective process, reducing the potential effectiveness of the funding on research activities.
A retrospective analysis of the clinical case records of ‘autistic psychopaths’ diagnosed by Hans Asperger and his team at the University Children's Hospital, Vienna
Authors: Hippler Kathrin , Klicpera Christian
Published: March 2003

To date, it is questionable whether the diagnostic criteria for Asperger syndrome (AS) as stated by ICD–10 or DSM–IV still reflect Asperger's original account of ‘autistic psychopathy’ (AP) from the 1940s. The present study examined 74 clinical case records of children with AP diagnosed by Hans Asperger and his team at the Viennese Children's Clinic and Asperger's private practice between 1950 and 1986. The characteristic features of the children are outlined, including reasons for referral, parental background, behavioural problems, cognitive functioning, communication and interests. Results show that the patients of Asperger described in our study represent a subgroup of children with very high intellectual functioning, specific circumscribed interests and talents but impaired social, communication and motor skills. Sixty–eight percent of the sample met ICD–10 criteria for AS, while 25% fulfilled the diagnostic criteria for autism. Implications for the diagnosis of AS are discussed.
Identifying neurocognitive phenotypes in autism
Authors: Tager-Flusberg Helen , Joseph Robert M.
Published: March 2003

Autism is a complex disorder that is heterogeneous both in its phenotypic expression and its etiology. The search for genes associated with autism and the neurobiological mechanisms that underlie its behavioural symptoms has been hampered by this heterogeneity. Recent studies indicate that within autism, there may be distinct subgroups that can be defined based on differences in neurocognitive profiles. This paper presents evidence for two kinds of subtypes in autism that are defined on the basis of language profiles and on the basis of cognitive profiles. The implications for genetic and neurobiological studies of these subgroups are discussed, with special reference to evidence relating these cognitive phenotypes to volumetric studies of brain size and organization in autism.
Why is joint attention a pivotal skill in autism?
Authors: Charman Tony
Published: March 2003

Joint attention abilities play a crucial role in the development of autism. Impairments in joint attention are among the earliest signs of the disorder and joint attention skills relate to outcome, both in the ‘natural course’ of autism and through being targeted in early intervention programmes. In the current study, concurrent and longitudinal associations between joint attention and other social communication abilities measured in a sample of infants with autism and related pervasive developmental disorders at age 20 months, and language and symptom severity at age 42 months, were examined. Extending the findings from previous studies, joint attention ability was positively associated with language gains and (lower) social and communication symptoms, and imitation ability was also positively associated with later language. Some specificity in the association between different aspects of joint attention behaviours and outcome was found: declarative, triadic gaze switching predicted language and symptom severity but imperative, dyadic eye contact behaviours did not. Further, although joint attention was associated with later social and language symptoms it was unrelated to repetitive and stereotyped symptoms, suggesting the latter may have a separate developmental trajectory. Possible deficits in psychological and neurological processes that might underlie the impaired development of joint attention in autism are discussed.
The enactive mind, or from actions to cognition: lessons from autism
Authors: Klin Ami , Jones Warren , Schultz Robert , Volkmar Fred
Published: March 2003

Normative–IQ individuals with autism are capable of solving explicit social cognitive problems at a level that is not matched by their ability to meet the demands of everyday social situations. The magnitude of this discrepancy is now being documented through newer techniques such as eye tracking, which allows us to see and measure how individuals with autism search for meaning when presented with naturalistic social scenes. This paper offers an approach to social cognitive development intended to address the above discrepancy, which is considered a key element for any understanding of the pathophysiology of autism. This approach, called the enactive mind (EM), originates from the emerging work on ‘embodied cognitive science’, a neuroscience framework that views cognition as bodily experiences accrued as a result of an organism's adaptive actions upon salient aspects of the surrounding environment. The EM approach offers a developmental hypothesis of autism in which the process of acquisition of embodied social cognition is derailed early on, as a result of reduced salience of social stimuli and concomitant enactment of socially irrelevant aspects of the environment.
Disentangling weak coherence and executive dysfunction: planning drawing in autism and attention–deficit/hyperactivity disorder
Authors: Booth Rhonda , Charlton Rebecca , Hughes Claire , Happé Francesca
Published: March 2003

A tendency to focus on details at the expense of configural information, ‘weak coherence’, has been proposed as a cognitive style in autism. In the present study we tested whether weak coherence might be the result of executive dysfunction, by testing clinical groups known to show deficits on tests of executive control. Boys with autism spectrum disorders (ASD) were compared with age– and intelligence quotient (IQ)–matched boys with attention–deficit/hyperactivity disorder (ADHD), and typically developing (TD) boys, on a drawing task requiring planning for the inclusion of a new element. Weak coherence was measured through analysis of drawing style. In line with the predictions made, the ASD group was more detail–focused in their drawings than were either ADHD or TD boys. The ASD and ADHD groups both showed planning impairments, which were more severe in the former group. Poor planning did not, however, predict detail–focus, and scores on the two aspects of the task were unrelated in the clinical groups. These findings indicate that weak coherence may indeed be a cognitive style specific to autism and unrelated to cognitive deficits in frontal functions.
The systemizing quotient: an investigation of adults with Asperger syndrome or high–functioning autism, and normal sex differences
Authors: Baron-Cohen Simon , Richler Jennifer , Bisarya Dheraj , Gurunathan Nhishanth , Wheelwright Sally
Published: March 2003

Systemizing is the drive to analyse systems or construct systems. A recent model of psychological sex differences suggests that this is a major dimension in which the sexes differ, with males being more drawn to systemize than females. Currently, there are no self–report measures to assess this important dimension. A second major dimension of sex differences is empathizing (the drive to identify mental states and respond to these with an appropriate emotion). Previous studies find females score higher on empathy measures. We report a new self–report questionnaire, the Systemizing Quotient (SQ), for use with adults of normal intelligence. It contains 40 systemizing items and 20 control items. On each systemizing item, a person can score 2, 1 or 0, so the SQ has a maximum score of 80 and a minimum of zero. In Study 1, we measured the SQ ofn= 278 adults (114 males, 164 females) from a general population, to test for predicted sex differences (male superiority) in systemizing. All subjects were also given the Empathy Quotient (EQ) to test if previous reports of female superiority would be replicated. In Study 2 we employed the SQ and the EQ withn= 47 adults (33 males, 14 females) with Asperger syndrome (AS) or high–functioning autism (HFA), who are predicted to be either normal or superior at systemizing, but impaired at empathizing. Their scores were compared withn= 47 matched adults from the general population in Study 1. In Study 1, as predicted, normal adult males scored significantly higher than females on the SQ and significantly lower on the EQ. In Study 2, again as predicted, adults with AS/HFA scored significantly higher on the SQ than matched controls, and significantly lower on the EQ than matched controls. The SQ reveals both a sex difference in systemizing in the general population and an unusually strong drive to systemize in AS/HFA. These results are discussed in relation to two linked theories: the ‘empathizing–systemizing’ (E–S) theory of sex differences and the extreme male brain (EMB) theory of autism.
Understanding autism: insights from mind and brain
Authors: Hill Elisabeth L. , Frith Uta
Published: March 2003

Autism is a developmental disorder characterized by impaired social interaction and communication as well as repetitive behaviours and restricted interests. The consequences of this disorder for everyday life adaptation are extremely variable. The general public is now more aware of the high prevalence of this lifelong disorder, withca. 0.6% of the population being affected. However, the signs and symptoms of autism are still puzzling. Since a biological basis of autism was accepted, approaches from developmental cognitive neuroscience have been applied to further our understanding of the autism spectrum. The study of the behavioural and underlying cognitive deficits in autism has advanced ahead of the study of the underlying brain abnormalities and of the putative genetic mechanisms. However, advances in these fields are expected as methodological difficulties are overcome. In this paper, recent developments in the field of autism are outlined. In particular, we review the findings of the three main neuro–cognitive theories of autism: theory–of–mind deficit, weak central coherence and executive dysfunction.
Investigating individual differences in brain abnormalities in autism
Authors: Salmond C. H. , de Haan M. , Friston K. J. , Gadian D. G. , Vargha-Khadem F.
Published: March 2003

Autism is a psychiatric syndrome characterized by impairments in three domains: social interaction, communication, and restricted and repetitive behaviours and interests. Recent findings implicate the amygdala in the neurobiology of autism. In this paper, we report the results of a series of novel experimental investigations focusing on the structure and function of the amygdala in a group of children with autism. The first section attempts to determine if abnormality of the amygdala can be identified in an individual using magnetic resonance imagingin vivo. Using single–case voxel–based morphometric analyses, abnormality in the amygdala was detected in half the children with autism. Abnormalities in other regions were also found. In the second section, emotional modulation of the startle response was investigated in the group of autistic children. Surprisingly, there were no significant differences between the patterns of emotional modulation of the startle response in the autistic group compared with the controls.
Introduction
Authors: Frith Uta , Hill Elisabeth L.
Published: March 2003

Although we know much more now than we did 50 years ago about autism, the nature, origin and even the definition of the condition are still debated and remain largely unknown. This special issue begins with a review of the facts about autistic disorders, as they are known at present. In their introduction, Elizabeth Hill & Uta Frith (2003) remind the reader that autism is no longer regarded as a rare disease. They provide examples of genetic and brain research that targets the biological causes of autism and they review the three major cognitive theories that are currently used to explain the core signs and symptoms of autism. Much more is known now about autism than was known only a few years ago, and there is justified hope that our understanding of autism will continue to accelerate at a fast pace. This issue contains examples of the cutting edge of research and highlights some of the most burning questions. Some of these relate to the diagnosis of Asperger syndrome (AS), the identification of subgroups in the autism spectrum and early signs of autistic disorder. Other questions relate to the brain abnormalities that underlie the putative cognitive deficits and whether these can be made visible through magnetic resonance imaging. The shared assumption among the contributors is that autism is a neurodevelopmental disorder that gives us a unique window on the relationship between mind and brain. The research reported elaborates the key theories that have been put forward to explain the signs and symptoms of autism. These theories try to explain the selective impact of brain abnormality on some of the most high–level mental functions, such as social insight, empathy and information processing style.