bluuebunny/crossref_metadata_2025 huggingface dataset:
Depletion-mode ZnO nanowire field-effect transistor
Authors: Heo Y. W. , Tien L. C. , Kwon Y. , Norton D. P. , Pearton S. J. , Kang B. S. , Ren F.
Published: September 2004

Single ZnO nanowire metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated using nanowires grown by site selective molecular-beam epitaxy. When measured in the dark at 25°C, he depletion-mode transistors exhibit good saturation behavior, a threshold voltage of ∼−3V, and a maximum transconductance of order 0.3mS∕mm. Under ultraviolet (366nm) illumination, the drain–source current increase by approximately a factor of 5 and the maximum transconductance is ∼5mS∕mm. The channel mobility is estimated to be ∼3cm2∕Vs, which is comparable to that reported for thin film ZnO enhancement mode MOSFETs, and the on∕off ratio was ∼25 in the dark and ∼125 under UV illumination.
Piezoelectric and ferroelectric properties of 1-μm-thick lead zirconate titanate film fabricated by a double-spin-coating process
Authors: Park Gun-Tae , Choi Jong-Jin , Park Chee-Sung , Lee Jae-Wung , Kim Hyoun-Ee
Published: September 2004

Lead zirconate titanate (PZT) films were deposited on platinized silicon substrates by spin coating using PZT sols containing polyvinylpyrrolidone (PVP) as an additive. Single-layered 1-μm-thick PZT films with 60∕40 composition were fabricated using two successive spin coatings followed by a single heat treatment step. The crack formation was effectively suppressed by the presence of nanosized pores which were generated during the heat treatment. The film has a preferred orientation corresponding to the (100) crystallographic direction. The ferroelectric and piezoelectric properties of the specimen were comparable to those of a film with same composition and thickness but prepared by the conventional sol-gel procedure.
Ferroelectricity of single-crystalline, monodisperse lead zirconate titanate nanoparticles of 9 nm in diameter
Authors: Seol Kwang Soo , Takeuchi Kazuo , Ohki Yoshimichi
Published: September 2004

Ferroelectric hysteresis at approximately 20 °C is measured in a lead zirconate titanate film prepared by stacking monodisperse and perovskite particles 9 nm in diameter. The particle-stacked film possesses a remanent polarization of 4.5μC∕cm2 and an apparent coercive field of 250 kV/cm. This result demonstrates that particulate lead zirconate titanate of 9 nm in diameter retains ferroelectricity even at room temperature.
Formation and thermal stability of sub-10-nm carbon templates on Si(100)
Authors: Guise Olivier , Ahner Joachim , Yates John , Levy Jeremy
Published: September 2004

We report a lithographic process for creating high-resolution (<10nm) carbon templates on Si(100). A scanning electron microscope, operating under low vacuum (10−6mbar), produces a carbon-containing deposit (“contamination resist”) on the silicon surface via electron-stimulated dissociation of ambient hydrocarbons, water, and other adsorbed molecules. Subsequent annealing at temperatures up to 1320K in ultrahigh vacuum removes SiO2 and other contaminants, with no observable change in dot shape. The annealed structures are compatible with subsequent growth of semiconductors and complex oxides. Carbon dots with diameter as low as 3.5nm are obtained with a 200μs electron-beam exposure time.
A magnetic trap for living cells suspended in a paramagnetic buffer
Authors: Winkleman Adam , Gudiksen Katherine L. , Ryan Declan , Whitesides George M. , Greenfield Derek , Prentiss Mara
Published: September 2004

This manuscript describes the fabrication and use of a three-dimensional magnetic trap for diamagnetic objects in an aqueous solution of paramagnetic ions; this trap uses permanent magnets. It demonstrates trapping of polystyrene spheres, and of various types of living cells: mouse fibroblast (NIH-3T3), yeast (Saccharomyces cerevisiae), and algae (Chlamydomonas reinhardtii). For a 40mM solution of gadolinium (III) diethylenetriaminepentaacetic acid (Gd·DTPA) in aqueous buffer, the smallest cell (particle) that could be trapped had a radius of ∼2.5μm. The trapped particle and location of the magnetic trap can be translated in three dimensions by independent manipulation of the permanent magnets. This letter a1so characterizes the biocompatibility of the trapping solution.
Photoluminescence measurements to study conductance switching and data storage in polythiophene based devices
Authors: Botta Chiara , Mercogliano Clara , Bolognesi Alberto , Majumdar Himadri S. , Pal Amlan J.
Published: September 2004

We have fabricated devices based on oriented thin film of a conjugated polymer, namely a polythiophene derivative, which exhibited the presence of two conducting states and switching between the states. Conductance switching in such devices has been studied by photoluminescence (PL) measurements. Depending on the conducting state of the polymer, the PL intensity of the polymer showed switching between high and low values. Both the conducting states displayed an associated memory for data-storage applications. We have shown that the induced states of the polymer, which are retained for more than 2h, can be read by the contact-less and nondestructive PL measurement.
Enhancement in ordering of FePt films by magnetic field annealing
Authors: Wang H. Y. , Ma X. K. , He Y. J. , Mitani S. , Motokawa M.
Published: September 2004

Effect of magnetic field annealing on chemical ordering of FePt films has been investigated. It is found that the ordering rate in FePt films is enhanced by applying a magnetic field during postdeposition annealing. Measurements of the structure and magnetic properties of FePt films reveal that the disorder–order transformation starts at or below 450°C when the film is annealed in a magnetic field of 40kOe. The possible reason for the enhancement in the ordering of FePt films by magnetic field annealing is discussed.
Microstructure and thermal stability of HfO2 gate dielectric deposited on Ge(100)
Authors: Gusev E. P. , Shang H. , Copel M. , Gribelyuk M. , D’Emic C. , Kozlowski P. , Zabel T.
Published: September 2004

We report on physical and electrical characterization of ultrathin (3–10nm) high-κHfO2 gate stacks deposited on Ge(100) by atomic-layer deposition. It is observed that uniform films of HfO2 can be deposited on Ge without significant interfacial growth. The lack of an interlayer enables quasiepitaxial growth of HfO2 on the Ge surface after wet chemical treatment whereas a nitrided interface (grown by thermal oxynitridation in ammonia) results in an amorphous HfO2. The stacks exhibit surprisingly good thermal stability, up to temperatures only 150°C below the melting point of Ge. In terms of electrical properties, HfO2 on Ge shows significantly reduced (up to 4 decades) gate leakage currents in the ultrathin regime of equivalent electrical thickness down to ∼1.4nm due to the high-dielectric constant of ∼23. Nitrided interface is observed to be important for good insulating properties of the stack.
Uncompensated spins in a micro-patterned CoFeB/MnIr exchangebias system
Authors: Eimüller T. , Kato T. , Mizuno T. , Tsunashima S. , Quitmann C. , Ramsvik T. , Iwata S. , Schütz G.
Published: September 2004

The element specific domain configuration of a microstructured Co86Fe10B4∕Mn77Ir23∕Ni80Fe20∕Si3N4 exchange bias film was studied by photoemission electron microscopy using x-ray magnetic circular dichroism. In the dots the magnetization shows less preferred orientation along the exchange bias direction than in unstructured areas. Uncompensated Mn spins at the CoFeB/MnIr interface with an antiferromagnetic coupling between the Mn and the Co magnetic moments could be studied by imaging and spectromicroscopy.
Screening-photovoltaic bright solitons in lithium niobate and associated single-mode waveguides
Authors: Fazio E. , Renzi F. , Rinaldi R. , Bertolotti M. , Chauvet M. , Ramadan W. , Petris A. , Vlad V. I.
Published: September 2004

Photorefractive screening-photovoltaic solitons are observed in lithium niobate. Two-dimensional bright circular solitons are formed thanks to a strong static bias field, externally applied, opposite to the photovoltaic internal field. The dynamics of the soliton formation is monitored and compared to a time-dependent numerical model allowing determination of the photovoltaic field. Efficient single mode waveguides are shown to be memorized by the soliton beam for a long time.
Bonding silicon-on-insulator to glass wafers for integrated bio-electronic circuits
Authors: Kim Hyun S. , Blick Robert H. , Kim D. M. , Eom C. B.
Published: September 2004

We report a method for bonding silicon-on-insulator wafers onto glass wafers. After pre-cleaning the wafers by an ozone and ultraviolet exposure, followed by mega-sonic water rinse, the SOI wafers are bonded to glass wafers in a vacuum chamber. This is performed at a temperature of 400 °C under an applied voltage of 700 V. The interface between the glass and SOI wafer is tested mechanically and inspected by electron beam microscopy. Furthermore, we demonstrate removal of the silicon bulk layer after wafer bonding. The quality of the single crystalline Si thin film on the glass wafers has been verified by four-circle x-ray diffraction and scanning electron microscopy. This process will allow us the integration of thin-film electronics in biological sensor applications.
Multi-dot floating-gates for nonvolatile semiconductor memories: Their ion beam synthesis and morphology
Authors: Müller T. , Heinig K.-H. , Möller W. , Bonafos C. , Coffin H. , Cherkashin N. , Assayag G. Ben , Schamm S. , Zanchi G. , Claverie A. , Tencé M. , Colliex C.
Published: September 2004

Scalability and performance of current flash memories can be improved substantially by replacing the floating polycrystalline-silicon gate by a layer of Si dots. Here, we present both experimental and theoretical studies on ion beam synthesis of multi-dot layers consisting of Si nanocrystals (NCs) embedded in the gate oxide. Former studies have suffered from the weak Z contrast between Si and SiO2 in transmission electron microscopy (TEM). This letter maps Si plasmon losses with a scanning TEM equipped with a parallel electron energy loss spectroscopy system. Kinetic Monte Carlo simulations of Si phase separation have been performed and compared with Si plasmon maps. Predicted and measured Si morphologies agree remarkably well, both change with increasing ion fluence from isolated NCs to spinodal pattern. However, the predicted fluences are lower than the experimental ones. We identify as the main reason of this discrepancy the partial oxidation of implanted Si by atmospheric humidity, which penetrates into the as-implanted SiO2.
A hydrothermally deposited epitaxial lead titanate thin film on strontium ruthenium oxide bottom electrode
Authors: Morita Takeshi , Cho Yasuo
Published: September 2004

A lead titanate epitaxial thin film was obtained on a strontium ruthenium oxide bottom electrode by the hydrothermal method. The reaction temperature was 150°C more than 400 degrees lower than that of the conventional deposition processes. X-ray diffraction measurements revealed a c-axis of orientation. The single-crystal-like DE hysteresis curve showed a remanent polarization of 96.5μC∕cm2. The domain direction was controlled by an applied electric field using a metal-coated atomic force microcopy cantilever probe and the domain pattern was observed by scanning nonlinear dielectric microscopy. This investigation verified that this film did not contain an a-domain. In addition, no defects such as domain or grain boundaries were observed, even on the nanoscale.
Photoluminescence of Eu-doped GaN thin films prepared by radio frequency magnetron sputtering
Authors: Shirakata Sho , Sasaki Ryo , Kataoka Takashi
Published: September 2004

The Eu-doped GaN thin films (GaN:Eu) were deposited on the sapphire substrate by means of the rf magnetron sputtering method. The GaN:Eu films were characterized by x-ray diffraction, scanning electron microscope, and photoluminescence (PL). Although as-grown GaN:Eu films (2mol% Eu in target) exhibited weak broad Eu-related red PL, the annealing in NH3 atmosphere (1000°C for 1h) led to the remarkable enhancement of Eu-related PL lines. PL spectra of such annealed GaN:Eu films exhibited a series of sharp PL lines characteristic of substitutional Eu3+ ions at Ga sites in the GaN lattice (dominant PL line is at 622nm for the D05–F27 transition). On the other hand for GaN:Eu films (5mol% Eu in target), as-grown films are amorphous and exhibited broad Eu3+-related PL lines. The annealing led to the crystallization of the films, the elimination of Eu3+-related PL lines, and the enhancement of the near-band-edge PL. The Eu-luminescent centers are considered to be removed during the crystallization.
Charge recombination electroluminescence in organic thin-film devices without charge injection from external electrodes
Authors: Tsutsui Tetsuo , Lee Sang-Bong , Fujita Katsuhiko
Published: September 2004

Organic thin-film electroluminescent (EL) devices with a double-insulated structure, Al electrode/polymer insulator layer/ambipolar EL layer/ITO nanoparticles layer/ambipolar EL layer/polymer insulator layer/ITO electrode, were fabricated. The ambipolar EL layer was the composition of poly (N-vinylcarbazole) as a hole transport material and 2,5-bis(4-naphthyl)-1,3,4-oxadiazole as an electron transport material in 65∕35 molar ratio with added 0.6mole% coumarin-6 for emissive centers. When the devices were driven with ac voltage, bright surface emission (81cd∕m2 at 250V and 300kHz) was observed. Emission is due to the recombination of holes and electrons that are generated from ITO nanoparticles embedded in organic layers. Charge recombination EL is observed without charge injection from external electrodes in double-insulated organic EL devices.
Coherent states in a coupled quantum dot nanocrystalline silicon transistor
Authors: Khalafalla M. A. H. , Durrani Z. A. K. , Mizuta H.
Published: September 2004

We investigate the coherent coupling of electronic states in a nanocrystalline silicon quantum dot transistor. The device consists of a nanometer-scale point-contact containing only a few silicon grains. The grains form quantum dots, tunnel-coupled across thin silicon sub-oxide grain boundaries. At 4.2K, we observe a pattern of single-electron conductance peaks versus two gate voltages, caused by electrostatic coupling between the quantum dots. Additional peaks are observed when the energy levels from two adjacent quantum dots are resonant, which may be associated with “quasi-molecular” states formed by coherent coupling of the levels. The tunnel splitting obtained from the peak separation is ∼0.4meV, which is from a few times to an order-of-magnitude larger than reported previously in GaAs∕AlGaAs quantum dots.
Acceptor-bound exciton transition in Mg-doped AlN epilayer
Authors: Nepal N. , Nakarmi M. L. , Nam K. B. , Lin J. Y. , Jiang H. X.
Published: September 2004

Mg -doped AlN epilayers grown by metalorganic chemical-vapor deposition have been studied by deep ultraviolet time-resolved photoluminescence (PL) spectroscopy. A PL emission line at 6.02eV has been observed at 10K in Mg-doped AlN, which is about 40meV below the free-exciton transition in undoped AlN epilayer. Temperature dependence of the PL intensity of this emission line also reveals a binding energy of 40meV. This transition line is believed to be due to the recombination of an exciton bound to neutral Mg acceptor (I1) with a binding energy of Ebx=40meV. This value is also about 10% of the energy level of Mg impurity in AlN satisfying Haynes’ rule. The recombination lifetime of the I1 transition in Mg-doped AlN has been measured to be 130ps, which is close to the expected value. The larger Ebx of the acceptor-bound exciton in AlN than that in GaN is due to large effective masses of the electrons and holes, as well as the energy level of Mg impurity.
250
nm
AlGaN
light-emitting diodes
Authors: Adivarahan V. , Sun W. H. , Chitnis A. , Shatalov M. , Wu S. , Maruska H. P. , Khan M. Asif
Published: September 2004

We report AlGaN deep ultraviolet light-emitting diodes (LEDs) at 250 and 255nm that have short emission wavelengths. For an unpackaged 200×200μm square geometry LED emitting at 255nm, we measured a peak power of 0.57mW at 1000mA of pulsed pump current. For a similar device emitting at 250nm the peak output power of 0.16mW was measured at 300mA of pulsed pump current. Progress is based on the development of high quality AlGaN cladding layers with an Al content up to 72%, which were grown over AlGaN∕AlN superlattice buffer layers on sapphire substrates. These n-Al0.72Ga0.28N layers were doped with Si up to about 1×1018cm−3 and electron mobilities up to 50cm2∕V∙s were estimated. High resolution x-ray diffraction studies gave a narrow (002) rocking curve with full width at half maximum of only 133arcsec.
Electrically tunable liquid-crystal photonic crystal fiber
Authors: Du Fang , Lu Yan-Qing , Wu Shin-Tson
Published: September 2004

Tunable light switch using a photonic crystal fiber filled with nematic liquid crystal is demonstrated. The original band-gap-guiding fiber structure was transformed to a total internal reflection-guiding photonic crystal fiber by filling liquid crystal into the air core and cladding air holes. By applying external voltage to the liquid-crystal-filled fiber, we have demonstrated an electrically tunable fiber-optical switch with over 30dB attenuation at 60Vrms for a He-Ne laser beam. This liquid-crystal-filled photonic crystal fiber will find useful applications in fiber-optic communication systems.
Suitability of epitaxial GaAs for x-ray imaging
Authors: Sun G. C. , Talbi N. , Verdeil C. , Bourgoin J. C.
Published: September 2004

Because the rate of indirect photon-electron conversion for scintillator materials coupled with arrays of photodiodes is at least 25 times smaller than the rate of direct conversion, we examine the conditions to be fulfilled by semiconductors undergoing such direct conversion to be applied to x-ray imaging. Bulk grown materials are not well suited to this application, because large defect concentrations give rise to strongly nonuniform electronic properties. We argue that only epitaxial layers are suitable for use as imaging devices and we illustrate our argument using the case of thick epitaxial GaAs layers. Detectors made with such layers exhibit a good energy resolution, a charge collection efficiency which approaches 1, linearity over more than three orders of amplitude, no afterglow (a response time shorter than 20 μs), and no charge-induced polarization effects.
Classification of the equilibrium states of a superfluid liquid with d pairing
Authors: Ivashin A. P. , Kovalevsky M. Y. , Chekanova N. N.
Published: September 2004

A classification of the equilibrium states of a quantum liquid with d pairing is given on the basis of the concept of quasi-averages. The order-parameter operator is represented in terms of Fermi operators. It is shown that the set of such equilibrium states can be classified in terms of the quantum number corresponding to the projection of the orbital angular momentum of a Cooper pair on the anisotropy direction. The explicit form of the three admissible generators of the unbroken symmetry is found and the corresponding equilibrium values of the order parameter are obtained. A generalization to possible nonuniform equilibrium structures is carried out, and the corresponding form of the order parameter of such structures is found.
Features of the low-temperature magnetic-field-induced order–order transitions in alloys of the system Fea−xMnxAs with a⩽1.6
Authors: Asadov S. K. , Val’kov V. I. , Zavadskii E. A. , Kamenev V. I. , Todris B. M.
Published: September 2004

Spontaneous and magnetic-field-induced first-order transitions of the order–order type in Fe0.5Mn1.1As and Fe0.55Mn1.04As single crystals with the C38 lattice (symmetry space group P4/nmm) are investigated at hydrostatic pressures up to 7 kbar in the temperature range from 4.2 to 300 K. The temperature and field dependences of the magnetization at different values of the pressure are measured in static and pulsed magnetic fields. It is established on the basis of the results that the first-order transitions from a low-magnetic to a high-magnetic phase induced by magnetic field pulses at low temperatures are irreversible, but with a finite existence time of the high-magnetic phase. A qualitative explanation of the observed effect is proposed on the basis of the theory of magnetostrictive blocking of the formation of new-phase nuclei at first-order phase transitions.
Electronic mechanism of structural phase transitions in manganese arsenide
Authors: Val’kov V. I. , Golovchan A. V.
Published: September 2004

The spin-fluctuation theory of magnetism is generalized to magnets with complex crystal and magnetic structure. An expression is obtained for the free energy of a system of itinerant p and d electrons, which are described by the Hubbard Hamiltonian with the static displacements of the ion cores, which lead to a change of the lattice symmetry, taken into account. The calculation of the free energy is done using the approximation of uniform local fields. The approach developed is applied to a study of the concrete magnetic and structural order parameters in ferromagnetic MnAs at T=0. It is shown that the appearance of structural distortions of the initial nickel arsenide lattice (nonzero structural order parameter) leads to a lowering of the average energy of the band electrons. The competition of the energy of the electrons and of the ion–ion coupling can stabilize these distortions. The interaction of the structural and magnetic order parameters tends to suppress the structural distortions. It is shown that the appearance of magnetization in the system (spontaneous or magnetic-field induced) can lead to restoration of the initial nickel arsenide structure. Such a magnetostructural transition is observed experimentally.
Low-temperature features of thermodynamics of an open isotropic Heisenberg chain
Authors: Zvyagin A. A. , Makarova A. V.
Published: September 2004

Low-temperature magnetic susceptibility and specific heat of an antiferromagnetic Heisenberg chain with open boundary conditions are calculated with the help of the exact Bethe ansatz method. These characteristics behave with temperature in a different way from those of a periodic chain.
Current oscillations and N-shaped current–voltage characteristic in the manganite Sm1−xSrxMnO3
Authors: Kamilov I. K. , Aliev K. M. , Ibragimov Kh. O. , Abakarova N. S.
Published: September 2004

Samples of Sm1−xSrxMnO3 with x=0.425 and 0.450 are investigated experimentally at temperature of 77 K in pulsed and static electric E and magnetic H (up to 10 kOe) fields in the mutual orientations H∥E and H⊥E. N-shaped current–voltage characteristics and high-frequency (up to 3 MHz) oscillations of the current are observed.
Stochastic dynamics of nuclear magnetization in ferromagnets
Authors: Chotorlishvili L. L. , Ckhvaradze V. M.
Published: September 2004

The nonlinear dynamics of the nuclear magnetization in ferromagnets is studied with the use of numerical methods. An analytical solution for the nonlinear equations of momentum is obtained. It is shown that at a large value of the dynamic frequency shift an overlap of the nonlinear resonances and chaotization of the nuclear spin system can occur.
Size-induced structural transformations in argon clusters with a fivefold symmetry axis
Authors: Danylchenko O. G. , Kovalenko S. I. , Samovarov V. N.
Published: September 2004

An electron-diffraction study of the structure of free clusters of Ar is carried out in the interval of mean sizes N̄≈600–1500 atoms/cluster. The existence of an amorphous (polyicosahedral) phase in large rare gas clusters with N̄≈600–800 atoms/cluster is observed for the first time. It is shown that with increasing number of atoms in a cluster a transition to a multilayer icosahedral (ordered) phase occurs in a rather narrow size interval.
Telecommuting, Residential Location, and Commute-Distance Traveled: Evidence from State of California Employees
Authors: Mokhtarian Patricia L , Collantes Gustavo O , Gertz Carsten
Published: September 2004

This study analyzes retrospective data on telecommuting and residential and job location changes over a ten-year period, from 218 employees (62 current telecommuters, 35 former telecommuters, and 121 people who had never telecommuted) of six California state government agencies which had actively participated in the well-known pilot program of 1988–90. We compare estimates of the total commute person-miles traveled by telecommuters with those of nontelecommuters, on a quarterly basis. Key findings include the following. One-way commute distances were higher for telecommuters than for nontelecommuters, consistent with prior empirical evidence and with expectation. Average telecommuting frequency declined over time; several explanations are proposed, but cannot be properly tested with these data. The first two findings notwithstanding, the average quarterly per capita total commute distances were generally lower for telecommuters than for nontelecommuters, indicating that they telecommute often enough to more than compensate for their longer one-way commutes. We cannot say from these results whether the ability to telecommute is itself prompting individuals to move farther away, or whether telecommuting is simply more attractive to people who already live farther from work for other reasons. Even if the first is true, however, and telecommuting is the ‘problem’, it also appears to be the solution: that is, it enables people to achieve a desired but more distant residential location without a net increase in commute travel.
A Spatial Filtering Specification for the Autologistic Model
Authors: Griffith Daniel A
Published: September 2004

The autologistic model describes binary correlated data; its spatial version describes georeferenced binary data exhibiting spatial dependence. The conventional specification of a spatial autologistic model involves difficult-to-nearly-impossible computations to ensure that appropriate sets of probabilities sum to 1. Work summarized here accounts for spatial autocorrelation by including latent map pattern components as covariates in a model specification. These components derive from the surface zonation scheme used to aggregate attribute data, to construct a geographic weights matrix, and to evaluate geographic variability. The illustrative data analysis is based upon field plot observations for the pathogen Phytophthora capsici that causes disease in pepper plants. Results are compared with pseudolikelihood and Markov chain Monte Carlo estimation techniques, both for the empirical example and for two simulation experiments associated with it. The principal finding is that synthetic map pattern variables, which are eigenvectors computed for a geographic weights matrix, furnish an alternative, successful way of capturing spatial dependency effects in the mean response term of a logistic regression model, avoiding altogether the need to use other than traditional standard techniques to estimate model parameters.
Realism and the Nature of Theory: A Lesson from J H von Thünen for Economists and Geographers
Authors: Mäki Uskali
Published: September 2004

It is argued that J H von Thünen was a realist who deliberately used unrealistic assumptions to pursue a true account of a major aspect of the determination of agricultural land-use patterns. The assumptions of the simplest model of concentric rings are examined to show that this highly unrealistic model deserves a realist interpretation: the idealising assumptions serve the purpose of neutralising the impact of a number of factors on the land-use pattern and thereby help focus on the causal contribution of one major factor, namely distance from the market. It is von Thünen's conviction that this factor and its causal contribution are real rather than fictional, and that his basic model truthfully captured them. The potential truth of von Thünen's simplest model does not require that its assumptions are true nor that the representation of the resulting land-use pattern is true. This reading of von Thünen's theory is contrasted with the traditional fictionalist ‘as-if’ interpretation of Der isolierte Staat espoused by Hans Vaihinger, Peter Hall, and others. It is pointed out that economists and geographers both hold notions of realism that fail to accommodate von Thünen's realism. Although economists tend to conflate realism and realisticness and therefore fail to understand that realism is compatible with the use of unrealistic assumptions, human geographers have adopted highly specific ideas of realism that fail to do justice to von Thünen's theory. Because much of theorising in both disciplines follows the Thünian strategy, there is an important lesson to be learnt both for supporters and for opponents of that strategy.
Geographical Economics versus Economic Geography: Towards a Clarification of the Dispute
Authors: Marchionni Caterina
Published: September 2004

Geographical economics is a recent approach in economics aiming at introducing the ‘role of space’ into the mainstream of the discipline. Though interested in similar issues, economic geographers strongly criticise geographical economics. This paper puts such criticisms under scrutiny, taking Ron Martin's 1999 influential contribution as representative. A philosophically informed analysis of these criticisms brings forth possible misunderstandings in the dispute and hence assists both parties by making criticism and responses more incisive. If, as it seems at least in some geographers’ view, economic geographers are concerned with mechanisms and processes different from the abstract general economic mechanisms analysed by geographical economists, then complementarity between the two approaches turns out to be a possibility. This challenges both economic geographers and geographical economists because it asks them to go beyond methodological differences and establish whether the general and abstract mechanisms identified by the latter are compatible with those identified by the former. If so, further investigation on how they combine as to bring about real-world agglomeration is needed.
Hearing as a Way of Dwelling: The Active Sense-Making of Environmental Risk and Nuisance
Authors: Soneryd Linda
Published: September 2004

The goal of integrating a broad set of stakeholders and local knowledges in environmental decisionmaking can come into conflict with the aim of effectively regulating environmental change through the establishment of standardised methods. In this paper I explore public perceptions of environmental change as active sense-making with respect to a particular aspect of the environment—sounds and noise. I use a case study of an Environmental Impact Assessment (EIA) process for the planned extension of an airport in Sweden. I focus on how local citizens reacted to the issue of airport noise as discussed in the EIA, as well as on local perceptions of noise. Analysis of local peoples' perceptions of environmental change raises questions concerning the meaning of environmental protection versus individual rights, the population affected by a development, and the issue of financial compensation versus commitment to dialogue. These questions must be raised in order to assess whether EIA fulfils its goal of increasing dialogue and building more participatory structures within the planning process.
Merleau-Ponty's Phenomenology and the Body-in-Space Encounters of Visually Impaired Children
Authors: Allen Chris
Published: September 2004

In this paper I argue that new social geographies of impairment present a conceptually sophisticated, but limiting, view of the impaired body as a container of social disadvantage. They say much less about how people with impairments routinely exercise agency in everyday life vis-à-vis the restrictive sociospatial circumstances in which they find themselves. I address this problem by developing a phenomenology of visually impaired children's everyday body-in-space encounters with their home and urban environments. This illustrates the various and creative ways in which visually impaired children routinely exercise agency within their home and urban environments.
Oriental Travel, Arabian Kinship, and Ritual Sacrifice: William Robertson Smith and the Fundamental Institutions
Authors: Livingstone David N
Published: September 2004

The report of a ten-day expedition to the Arabian Hijaz by William Robertson Smith forms the fulcrum of an inquiry into the work of this denominated orientalist. A biblical scholar, encyclopedist, cultural anthropologist, and student of comparative religion, whose writings profoundly influenced figures such as Emile Durkheim, Sigmund Freud, and Bronislaw Malinowski, Smith's experiences in the Arabian peninsula were crucial in his efforts to understand the nature of early Semitic social life, particularly the role played by ritual sacrifice and kinship rules. In this paper I argue that Smith's tour must be read not as an exercise in the Occidental ‘othering’ of the Orient but as a project in self-understanding and as a set of investigations into the genealogy of the Christian West. As such it is used to engage with contemporary debates about orientalism.
Haptic Perception of Virtual Surfaces: Scaling Subjective Qualities and Interstimulus Differences
Authors: Hollins Mark , Seeger Adam , Pelli Gabriele , Taylor Russell
Published: September 2004

We examined, in two experiments, the perceptual scaling of the properties of haptically examined virtual surfaces, and the way in which these properties subjectively combine. Participants used a consistent movement pattern to explore, with a stylus, virtual surfaces generated by a force-feedback device. In experiment 1, four surface properties (bump size, friction, resistance to normal force, and vibration amplitude) were varied individually, in separate blocks of trials. Free magnitude estimates of the subjective dimensions corresponding to these properties showed that all four dimensions conformed closely to the power law, except at very low stimulus values. Exponents for bump size (0.80) and stiffness (1.01) were consistent with values established in earlier work with direct touch of real surfaces. Surprisingly, the exponent for stickiness, not previously measured, was much higher than those for other dimensions (1.49). In experiment 2, dimensional combinations were analyzed by asking subjects to give magnitude estimates of the subjective difference between pairs of surfaces differing in one or two properties. Magnitude estimates of a given one-dimensional difference were generally larger when the subject was pressing down firmly on the surfaces, than when only gentle downward pressure was required; this result suggests that forces generated when a surface is haptically examined are interpreted as invariant indicators of the magnitudes of the surface properties themselves. Estimates of one-dimensional differences were also used to make predictions of two-dimensional differences, under assumptions of dimensional integrality and separability. The results fell between these two sets of predictions, indicating only modest integration of surface properties examined with indirect touch.
Bottom-up and Top-down Control in Visual Search
Authors: van Zoest Wieske , Donk Mieke
Published: September 2004

Previous research suggests that the allocation of attention is largely controlled either in a stimulus-driven or in a goal-driven manner. To date, few studies have systematically manipulated variables affecting stimulus-driven and goal-driven selection independently in order to investigate how both manners of control interrelate and affect performance in visual search. In the present study observers were presented with search displays consisting of an array of line segments rotated at various orientations. The task of observers was to indicate the presence or absence of a vertical line segment (the target) presented amongst a series of nontargets and possibly one distractor. By varying the absolute differences in orientation between the target, nontargets, and distractors, relative target–distractor salience and target–distractor similarity were independently manipulated to investigate the contribution of stimulus-driven and goal-driven control. The major result was that relative target–distractor salience and target–distractor similarity affected search performance independently. Performance was better in cases where the irrelevant distractor was not a salient item in the search display and did not look similar to the target. The results are discussed in terms of models of attentional control.
Jitter and Size Effects on Vection are Immune to Experimental Instructions and Demands
Authors: Palmisano Stephen , Chan Amy Y C
Published: September 2004

Both coherent perspective jitter and explicit changing-size cues have been shown to improve the vection induced by radially expanding optic flow. We examined whether these stimulus-based vection advantages could be modified by altering cognitions and/or expectations about both the likelihood of self-motion perception and the purpose of the experiment. In the main experiment, participants were randomly assigned into two groups—one where the cognitive conditions biased participants towards self-motion perception and another where the cognitive conditions biased them towards object-motion perception. Contrary to earlier findings by Lepecq et al (1995 Perception24 435–449), we found that identical visual displays were less likely to induce vection in ‘object-motion-bias’ conditions than in ‘self-motion bias’ conditions. However, significant jitter and size advantages for vection were still found in both cognitive conditions (cognitive bias effects were greatest for non-jittering same-size control displays). The current results suggest that if a sufficiently large vection advantage can be produced when participants are expecting to experience self-motion, it is likely to persist in object-motion-bias conditions.
Solute accumulation and osmotic adjustment in leaves of Brassica oilseeds in response to soil water deficit
Authors: Ma Qifu , Turner David W. , Levy David , Cowling Wallace A.
Published: September 2004

To establish methods for improving drought tolerance in Brassica oilseeds, we examined the influence of soil water deficit on solute accumulation in expanded and expanding leaves. We assessed the contribution of individual solutes to osmotic adjustment (OA) and determined the effect of homozygosity on the variation of the expression of OA. Juvenile plants of canola (Brassica napus cvv. Karoo and Monty) and Indian mustard (B. juncea line PI-81792) were grown under glasshouse conditions. The 3 genotypes expressed similar magnitudes of OA in response to drought, compared with a 2-fold higher OA in expanding leaves than in fully expanded leaves. Drought-induced changes in OA of expanded leaves of all genotypes were largely due to the accumulation of nitrate (42−47%), soluble sugars (31−38%), and proline (11−14%). In expanding leaves, K+ accumulation was significant (23–27%) as was proline (17−22%), whereas nitrate and soluble sugars were less important than in expanded leaves. By comparison, ions of Na+, Cl–, and water-soluble Mg2+ and Ca2+ did not contribute significantly to OA. Proline was hardly detected in well watered plants, but sharply increased in leaves of droughted plants in direct proportion to the magnitude of OA (80 ± 7 mmol/MPa, r2 = 0.94). A comparison between doubled haploid (DH) and commercial seed sources of 2 B. napus cultivars showed similar mean values in OA. The DH lines had a 33% lower coefficient of variation in OA than cv. Karoo and 48% lower than cv. Monty among replicate plants. Proline may be a suitable ‘marker’ for OA in juvenile Brassica plants because of all the solutes measured, its concentration was directly proportional to the magnitude of OA across cultivars and leaf types. The use of DH lines will improve the precision in selection of genotypes that have the capacity to osmotically adjust under soil water deficit.
Modelling the transpiration of a greenhouse zucchini crop grown under a Mediterranean climate using the Penman-Monteith equation and its simplified version
Authors: Rouphael Youssef , Colla Giuseppe
Published: September 2004

In Mediterranean climates, high temperatures and vapour pressure deficits are currently observed in greenhouses during summer. These conditions are responsible for a high transpiration rate leading to greater water consumption. Measuring and modelling transpiration can be useful for efficient irrigation management by allowing prediction of short-term water demand. The rate of transpiration of zucchini crops (Cucurbita pepo L.) grown in soilless culture was measured in a greenhouse located at Viterbo, central Italy, during spring–summer 2002. The Penman-Monteith equation was used to predict the potential transpiration of the plants averaged over 30-min intervals using different approaches in the calculation of aerodynamic resistance. The values obtained were compared with transpiration measured by a gravimetric method by weighing plants on an electronic balance. Leaf temperature was lower (up to 5°C) than air temperature on clear summer days owing to high transpiration rates. Stomatal resistance was computed and found to be exponentially related to solar radiation. The best fit in transpiration between the Penman-Monteith calculated and those measured was achieved when the heat transfer in the former was obtained as a process of mixed convection, where the slope of the regression was 1, and there was improvement of the coefficient of determination (R2 = 0.96). A simplified model of daytime transpiration based on easily measured variables (solar radiation and vapour pressure deficit) was developed and produced strong agreement with the gravimetric method (R2 = 0.93).
Interrelationships between porcine somatotropin (pST), betaine, and energy level on body composition and tissue distribution of finisher boars
Authors: Suster D. , Leury B. J. , King R. H. , Mottram M. , Dunshea F. R.
Published: September 2004

Fifty-six individually penned boars (initial weight 64 kg) were used to investigate the interactions between dietary betaine, dietary energy, and porcine somatotropin (pST) treatment. The study was a 2 × 2 × 2 factorial experiment with the respective factors being dietary betaine (0 or 1.5 g/kg) and energy level (80% or 100% ad libitum) and treatment with pST (0 or 5 mg/day). A Hologic QDR4500A Dual Energy X-ray Absorptiometer (DXA) was used to determine body composition of pigs at the beginning and end of the study at Day 35. After slaughter, the composition of the whole half-carcass as well as the shoulder, ham, belly, and loin primal cuts was determined with DXA and verified with manual dissection. The main effects of dietary betaine were most pronounced when dietary energy was restricted. Under these conditions, daily gain was increased by dietary betaine (1188 v. 1271 g/day, P = 0.049) and pST (1115 v. 1344 g/day, P < 0.001). When dietary energy was restricted, lean tissue deposition was increased by dietary betaine (830 v. 908 g/day, P = 0.032) and pST (764 v. 974 g/day, P < 0.001), and these effects were additive. As a result, the lean meat yield in the half-carcass was increased by both dietary betaine (23.9 v. 25.1 kg, P = 0.043) and pST (23.3 v. 25.7 kg, P < 0.001). Lean tissue responses in primal cuts were more variable but followed a similar pattern. There was little effect of either dietary betaine or pST on fat deposition. These data demonstrate that when energy intake is limiting the potential for growth (as is normally the case for the improved boar), then both dietary betaine and pST treatment, either alone or in combination, can increase lean tissue deposition without increasing fat deposition.
Nitrate leaching from temperate perennial pastures grazed by dairy cows in south-eastern Australia
Authors: Eckard R. J. , White R. E. , Edis R. , Smith A. , Chapman D. F.
Published: September 2004

Nitrate (NO3-N) leaching losses were measured over 3 years from a temperate grass/clover pasture with and without 200 kg N fertiliser/ha, applied as ammonium nitrate or urea, using a system of moles and tile drains. Fertiliser was applied in 4 split dressings of 50 kg N/ha in each of the 4 seasons of each year. Drainage was collected continuously and NO3-N concentrations in drainage water were measured in subsamples collected using a flow-proportioned sampler. Pastures were rotationally grazed with dairy cows at stocking rates equivalent to 1.9 or 2.8 cows/ha for the unfertilised and fertilised treatments, respectively. Soil water deficit (SWD) varied markedly between seasons and years, with drainage occurring in the cooler, wetter months (April–October) and not at all through the summer. There were no significant differences between treatments in SWD, drainage events, or drainage volumes. Peak NO3-N concentrations were 19, 50, and 17 mg/L for the control, ammonium nitrate, and urea treatments, respectively. Mean annual flow-weighted NO3-N concentrations over the 3 years were 1.7 and 2.2 times higher from the ammonium nitrate treatment than from the urea and control treatments, respectively. Annual NO3-N leaching loads (kg N/ha) were 3.7–14.6 from the control treatment, 6.2– 22.0 from the urea treatment, and 4.3–37.6 from the ammonium nitrate treatment, for the lowest and highest drainage years, respectively. The experiment confirmed that the application of N fertiliser prior to periods of substantial drainage can result in high losses of NO3-N through leaching. More efficient and environmentally sound use of N fertiliser can be achieved by not combining high N fertiliser rates, high stocking intensity, and nitrate-containing fertilisers prior to periods when there is a risk of substantial drainage occurring.
Bentazone uptake into plant foliage as influenced by surfactants and carrier pH
Authors: Liu Z. Q.
Published: September 2004

The influence of surfactants and carrier pH on the foliar uptake of bentazone, a representative weak acid herbicide, was studied using bean (Vicia faba) and mustard (Sinapis alba) plants. The promoting effect of surfactants on bentazone uptake varied with surfactant hydrophobe structure, ethylene oxide (EO) content, and surfactant and bentazone concentrations. Among the 5 hydrophobe moieties tested, the efficiency order was C13 /C15 linear alcohols > C10 linear alcohol > C16 /C18 linear alcohols > nonylphenol > octylphenol. For C13 /C15 linear alcohol surfactants of differing EO content, the enhancing effect on bentazone uptake was 5 EO > 10 EO > 14 EO. All surfactants improved uptake more when bentazone was applied at low concentration. The effect of carrier pH (5, 7, and 9) on the uptake of bentazone, applied both as unformulated acid and as a sodium salt, was also investigated in this work. Lower carrier pH did not provide greater uptake for bentazone sodium salt and was only beneficial for the uptake of bentazone acid applied at very low concentration. The results are discussed in relation to the current knowledge on pesticide uptake as influenced by surfactants and the change in lipophilicity and solubility of weak acid chemicals at different pH.