bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress limits and minimum reinforcement requirements in shear design provisions
Authors: Kuchma Daniel A. , Su Kim Kang
Published: January 2005

There are substantial differences in the maximum stress limits and minimum shear reinforcement requirements that are used in codes of practice. A database of 1287 shear test results was used to evaluate the requirements/limits that are used in the ACI318‐02 Building Code, the AASHTO‐LRFD Bridge Design Specifications, and Eurocode 2. Owing to concerns and uncertainties about the behaviour of members cast with high‐strength concrete, codes of practice place a limit on the maximum concrete compressive strength (f′c) that may be used in design relationships. This limit may be as low as 50 MPa. An examination of test data reveals that these maximum stress limitations may be unnecessary, except for members that are large, lightly reinforced in flexure, and which do not contain shear reinforcement.

Codes also limit the maximum allowable shear stress in a member. In this case, the limitation is principally to guard against brittle compression failures. The shear stress limits employed in the three codes examined were found to differ by up to 2.5 times. This illustrates a lack of international agreement on fundamental issues related to shear behaviour. While only a limited amount of test data is available to evaluate the appropriateness of the selected limits, these data suggest that the ACI318‐02 limitation may be needlessly conservative.

Minimum shear reinforcing requirements also differ substantially between these three codes of practice. The test data indicate that there is a small positive correlation of the shear strength ratio (Vtest/Vcode) with the amount of shear reinforcement and little to no correlation of this ratio with the spacing of the shear reinforcement.

It is suggested that more accurate shear design provisions, minimum reinforcement requirements, and maximum shear limits will be achieved if researchers and code committee members work together to develop a qualified test database from which future research needs may be defined and from which improved provisions can be developed.
Evaluation of a scenario‐based reading technique for analysing process components
Authors: Tortorella Maria , Visaggio Giuseppe
Published: January 2005

To improve a working process, one or more process components can be replaced by innovative ones. The literature provides a possible source of innovative process components. However, it is often difficult to evaluate whether a particular innovative process component satisfying an improvement goal can be introduced to replace a process component in the working software process to be improved. In previous works, the authors of this paper proposed a characterization and evaluation framework to address the above problem. To improve the usability of the framework, a scenario was defined for each question to help the user answer it methodically. The experiment presented in this paper aims to verify if a scenario‐based reading technique improves the usability of the framework. The results obtained show that the technique proposed makes assessment of which process components of a working process are candidates for making innovation more reliable. Moreover, the scenario‐based reading technique is user independent and only a little training may be sufficient to sensibly improve the effectiveness of use of the scenarios. The trustworthy results of this technique and its independence of the user's previous knowledge and ability ensure that it can be applied methodically. Copyright © 2001 John Wiley & Sons, Ltd.
Interview with Girish Parikh
Authors: Parikh Girish , Chapin Ned
Published: January 2005

Girish Parikh describes the factors that influenced his extensive work in software maintenance. He overviews his major publications, describes his contributions to the field and their basis. Copyright © 2001 John Wiley & Sons, Ltd.
Multi‐modal systems method: the impact of normative factors on community viability
Authors: de Raadt Veronica D.
Published: January 2005

This is an analysis of viability in a small village in northern Sweden and a contribution to testing the multi‐modal systems method (MMSM). With the aid of the method, factors important to a village's life were selected and relationships between them analysed, to see if they promoted or threatened viability. Relationships are characteristic of a small community and it is argued that viability is best understood by examining relationships. MMSM proved a useful tool for studying relationships between the factors selected, between various modalities of community life, and between community groups. Copyright © 2001 John Wiley & Sons, Ltd.
GSM‐IP: A VoIP service for mobile networks
Authors: Pang Ai‐Chun , Lin Yi‐Bing , Chang Ming‐Feng
Published: January 2005

Based on media gateway control protocol (MGCP), this paper describes GSM‐IP, a voice over IP service for GSM mobile network. With the signaling protocol translation mechanism provided by the MGCP signaling gateway, we demonstrate how to interwork the MGCP elements with the home location register, visitor location register and mobile switching center in the GSM network. Then we present the message flows for GSM‐IP registration, call origination, call delivery, call release and inter‐system handoff procedures. We show the feasibility of integrating GSM with the MGCP‐based VoIP network without modifying the GSM network. Furthermore, our approach does not introduce new protocol primitives to MGCP. Copyright © 2001 John Wiley & Sons, Ltd.
Transition prediction for a two‐dimensional reynolds‐averaged navier–stokes method applied to wind turbine airfoils
Authors: Brodeur Robert R. , van Dam C. P.
Published: January 2005

Boundary layer transition is significant to many flow fields that include both laminar and turbulent regions. Accurate prediction of transition onset is fundamental to the modelling of these flows. In most flow solvers based on the Reynolds‐averaged Navier–Stokes equations, transition onset must be specified manually. To overcome this weakness and to more accurately predict aerodynamic flow fields, a boundary layer transition prediction methodology is presented. This methodology, which has been applied to a Navier–Stokes solver, dynamically locates transition onset as the flow solution is converging. The prediction methodology identifies several boundary layer transition mechanisms, including Tollmien–Schlichting instability, laminar separation and turbulence contamination. Where possible, the implementation utilizes the calculated boundary layer velocity profiles to strongly couple the predicted transition locations and the flow solution. The transition prediction methodology was used to predicted transition onset for the NLF(1)‐0416 and S809 single‐element wind turbine airfoils. Results obtained with numerical calculations are found to agree well with experimental observations. Copyright © 2001 John Wiley & Sons, Ltd.
Prey–predator mutualism in a tritrophic system on a camphor tree
Authors: Kasai Atsushi , Yano Shuichi , Takafuji Akio
Published: January 2005

We report the discovery of a mutualistic system encompassing prey–predator interactions. A domatium is a small space in a vein axil on the underside of leaves of woody angiosperms. Cinnamomum camphora Linn. has domatia that harbor a microphytophagous eriophyid mite (sp. 1). We previously reported that a predatory mite, Euseius sojaensis (Ehara), depends on this eriophyid mite as food. We revealed that E. sojaensis also preyed upon another eriophyid mite (sp. 2) that induces galls on leaves, and that the mean area of C. camphora leaves with galls was usually less than half that of leaves without galls. We experimentally tested the effect of E. sojaensis on galls, and confirmed that the presence of E. sojaensis reduced gall induction. Therefore, C. camphora, eriophyid mite sp. 1, and E. sojaensis comprise a mutualistic system, in spite of the prey–predator interactions among them. The conventional concept of mutualism does not apply to such prey–predator interactions, so we defined them as “systematic mutualism.” Here, the system consists of three trophic levels, and individuals that constitute this system benefit from the other species that constitute this system.
Comparisons of germination traits of alpine plants between fellfield and snowbed habitats
Authors: Shimono Yoshiko , Kudo Gaku
Published: January 2005

We examined the seed‐germination responses of 27 alpine species with reference to habitat type (fellfield and snowbed), temperature (five regimes), and light requirement. About 70% of species showed >40% germination at warm temperatures without cold stratification. However, a moist‐chilling treatment markedly improved the germination percentages in most species, especially under cool conditions. Thus, cold stratification effectively reduced the temperature requirement for germination. Patterns of germination response within species were not consistent between the fellfield and snowbed habitats for species inhabiting both habitats. For interspecific comparisons, there were no significant differences in germination responses to the temperature regimes and the cold stratification between the fellfield and snowbed species. Also, germination speed and the length of germinating period did not differ between fellfield and snowbed species. Most species (86%) showed a requirement for light for germination without cold stratification. Although the extent of the light requirement was reduced after cold stratification in some species, the light requirement of most small‐seeded species remained. The combination of cold stratification and the light requirement is a major factor determining the seedling emergence and formation of seed banks in alpine plants. However, habitat‐specific patterns of germination traits were less clear, suggesting similar germination traits in fellfield and snowbed plants, at least under controlled conditions in the laboratory.
Assessment of the anthelmintic effect of natural plant cysteine proteinases against the gastrointestinal nematode,Heligmosomoides polygyrus,in vitro
Authors: STEPEK G. , BUTTLE D. J. , DUCE I. R. , LOWE A. , BEHNKE J. M.
Published: January 2005

We examined the mechanism of action and compared the anthelmintic efficacy of cysteine proteinases from papaya, pineapple, fig, kiwi fruit and Egyptian milkweedin vitrousing the rodent gastrointestinal nematodeHeligmosomoides polygyrus. Within a 2 h incubation period, all the cysteine proteinases, with the exception of the kiwi fruit extract, caused marked damage to the cuticle ofH. polygyrusadult male and female worms, reflected in the loss of surface cuticular layers. Efficacy was comparable for both sexes of worms, was dependent on the presence of cysteine and was completely inhibited by the cysteine proteinase inhibitor, E-64. LD50values indicated that the purified proteinases were more efficacious than the proteinases in the crude latex, with purified ficin, papain, chymopapain, Egyptian milkweed latex extract and pineapple fruit extract, containing fruit bromelain, having the most potent effect. The mechanism of action of these plant enzymes (i.e. an attack on the protective cuticle of the worm) suggests that resistance would be slow to develop in the field. The efficacy and mode of action make plant cysteine proteinases potential candidates for a novel class of anthelmintics urgently required for the treatment of humans and domestic livestock.
The sensitivity of Fanconi anaemia group C cells to apoptosis induced by mitomycin C is due to oxygen radical generation, not DNA crosslinking
Authors: CLARKE A. A. , PHILPOTT N. J. , GORDON‐SMITH E. C. , RUTHERFORD T. R.
Published: January 2005

Fanconi's anaemia (FA) is characterized by increased spontaneous and induced chromosome fragility. This has been widely regarded to be due to a defect in DNA crosslink repair, because of the sensitivity of cells to known DNA crosslinking agents such as mitomycin C (MMC) and diepoxybutane (DEB). Although Fanconi cells are also sensitive to molecular oxygen, and may be protected by antioxidants, this has generally been considered to be a secondary phenomenon. However, it has recently been demonstrated that the FAC protein, coded for by the Fanconi anaemia gene for complementation group C, is strictly cytoplasmic and does not enter the nucleus even after DNA damage, which seems inconsistent with a role in DNA repair.

We have studied the effects of MMC and oxygen on apoptotic cell death in FA group C (FA‐C) and normal lymphoblastoid cell lines. Hyperoxia alone failed to induce apoptosis in either FA‐C or normal cells. At ambient oxygen, MMC is known to generate oxygen free radicals, whereas decreased oxygen tension facilitates the metabolic activation of MMC for DNA crosslinking. We therefore studied the effects of MMC at 20% and 5% oxygen to favour oxygen radical generation or DNA crosslinking respectively. FA‐C cells showed increased sensitivity compared to normal cells for the induction of apoptosis by MMC at 20% oxygen. When cells were treated with MMC at 5% oxygen we found no increased sensitivity of Fanconi cells to MMC when compared to normal cells. These results imply a role for oxygen free radicals, but not for DNA crosslinking, in the sensitivity of FA cells to MMC.
Current image tunneling spectroscopy of boron-doped nanodiamonds
Authors: Cheng Hsiu-Fung , Lee Yen-Chih , Lin Su-Jien , Chou Yi-Ping , Chen Tom T. , Lin I-Nan
Published: January 2005

The electron field emission properties of the nanodiamond films were examined using scanning tunneling microscopic (STM) technique. Current image tunneling spectroscopic measurements reveal the direct dependence of electron tunneling/field emission behavior of the films on the proportion of grain boundaries present. Local tunneling current-voltage (It–V) measurements show that incorporation of boron species insignificantly alters the occupied state, but markedly modifies the empty state of the diamond films, viz. it induces the presence of impurity states for the films heavily doped with borons, resulting in smaller emission energy gap for the samples. Such a characteristic improves both the local electron field emission behavior of the diamond films measured by STM and the average electron field emission properties measured by conventional parallel plate setup. These results infer clearly that the presence of impurity states due to boron doping is a prime factor improving the field emission properties for these boron-doped nanodiamond films.
Dielectric behavior of Fe-ion-doped BaTiO3 nanoparticles
Authors: Jana A. , Kundu T. K. , Pradhan S. K. , Chakravorty D.
Published: January 2005

Iron-ion-doped barium titanate (BaTiO3) nanoparticles have been synthesized through a chemical route using polyvinyl alcohol. The polymer serves as a surfactant to encapsulate the cationic species in divided groups during the reaction that confines the size and morphology of the specimen. The concentration of Fe3+ varies from 0 to 2 mol % in the specimens. The results from x-ray diffractograms and transmission electron micrographs show that the particle diameters in the specimen lie in the range 29 to 49 nm. It is seen that the ferroelectric-paraelectric phase transition temperature (Tc) varies with the composition and the dielectric permittivity in doped specimens is enhanced by an order of magnitude compared to undoped barium titanate ceramics. The dielectric permittivity shows maxima in the specimen containing 0.3 mol % of dopant concentration. The dielectric behavior of the specimens is explained in terms of the change in crystalline structure of the specimens.
Gunn effect in field-emission phenomena
Authors: Litovchenko V. , Evtukh A. , Yilmazoglu O. , Mutamba K. , Hartnagel H. L. , Pavlidis D.
Published: January 2005

The peculiarities of electron field emission from nanostructured GaN surface have been investigated. The current–voltage characteristics of emission current in Fowler–Nordheim plot show two parts with different slopes. There are emission current oscillations in the changing slope region. As an explanation for the experimental results a model based on the electron-emission analysis from lower (Γ) valley, upper (U) valley, and electron transition between valleys due to heating in electric field has been proposed. The electron affinities for the emission from Γ and U valleys have been determined. The decreased affinities from there valleys have been estimated for quantization in nanostructured GaN.
Modeling room-temperature lasing spectra of 1.3-μm self-assembled InAs∕GaAs quantum-dot lasers: Homogeneous broadening of optical gain under current injection
Authors: Sugawara M. , Hatori N. , Ebe H. , Ishida M. , Arakawa Y. , Akiyama T. , Otsubo K. , Nakata Y.
Published: January 2005

We studied the injection current dependence of room-temperature lasing spectra of a 1.3-μm self-assembled InAs∕GaAs quantum-dot laser both experimentally and theoretically. Starting from the ground-state lasing with a few longitudinal modes, the spectra showed splitting, broadening, excited-state lasing, and quenching of the ground-state lasing as the current increased. We could explain this unique current dependence by numerical simulation based on our quantum-dot laser theory, taking into account the inhomogeneous and homogeneous broadening of the optical gain as well as the carrier relaxation processes in the spatially isolated quantum dots. Through the simulation, we found that the homogeneous broadening of the ground state is kept between 5 and 10 meV under the ground-state lasing, while it increases up to 20 meV under the excited-state lasing.
A model for multistep trap-assisted tunneling in thin high-k dielectrics
Authors: Blank O. , Reisinger H. , Stengl R. , Gutsche M. , Wiest F. , Capodieci V. , Schulze J. , Eisele I.
Published: January 2005

A model for multistep trap-assisted tunneling (TAT) with strong dependence on the trap concentration is introduced. The current density J as a function of the applied voltage V for A1/chemical vapor deposition-Al2O3∕SiO2∕p-Si structures has been measured and fitted for 12 orders of magnitude in a temperature range from T=42K to T=420K. A trap concentration of NT=1.3×1019∕cm3, an electron affinity of eχel=1.7eV, and an effective electron mass of mox=0.28m0 (m0 is the electron rest mass) for the Al2O3 are used. A single set of parameters fits the leakage currents of all samples with different Al2O3 thicknesses at all temperatures.
Temperature-induced voltage drop rearrangement and its effect on oxide breakdown in metal-oxide-semiconductor capacitor structure
Authors: Wang Tsung-Miau , Hwu Jenn-Gwo
Published: January 2005

This work studies the breakdown (BD) characteristics of metal-oxide-semiconductor (MOS) capacitors at various temperatures. The oxide thickness and temperature significantly affect the probability of BD. BD does not easily occur in ultrathin silicon dioxide when biased in the positive substrate injection region of MOS(p). However, the BD frequency increases dramatically with the oxide thickness or the temperature. The phenomenon was explained by temperature effect. When the temperature increases, the voltage drop across the silicon dioxide increases; on the contrary, the voltage across the (deep) depletion region in the Si substrate declines. Also, the enhancement of percolation and the increase in the number of interface states result in the more severe degradation of the silicon dioxide. Also, a thicker oxide has more Dit, and so undergoes degradation more easily. Finally, the C–V characteristics of the MOS capacitor in the (deep) depletion region are also discussed in order to understand the mechanisms among temperature, thickness, and percolation effect.
Buried stressors in nitride semiconductors: Influence on electronic properties
Authors: Romanov A. E. , Waltereit P. , Speck J. S.
Published: January 2005

An analysis is presented on the effect of the strain field originating from a subsurface stressor (point source of dilatation or a dilatating ellipsoidal inclusion) on the electronic properties of nitride semiconductors. With good accuracy, real quantum dots can be modeled as such stressors. We consider the following material structure design: a uniform semi-infinite GaN matrix with a buried stressor or a GaN matrix with a single (In,Ga)N quantum well, which is grown pseuodomorphically between the stressor and the free surface. We utilize isotropic elasticity to determine the strain field in the structures under investigation. We then apply a k∙p perturbation theory approach to examine the shifts of the conduction and valence band edges caused by the stressor. We find lateral confinement for electrons and holes, which can be proposed for the realization of strain-induced quantum dots in the quantum well.
Infrared detection of hydrogen-generated free carriers in polycrystalline ZnO thin films
Authors: Wolden Colin A. , Barnes Teresa M. , Baxter Jason B. , Aydil Eray S.
Published: January 2005

The changes in the free-carrier concentration in polycrystalline ZnO films during exposure to H2 and O2 plasmas were studied using in situ attenuated total reflection Fourier transform infrared spectroscopy. The carrier concentration and mobility were extracted from the free-carrier absorption in the infrared using a model for the dielectric function. The electron density in polycrystalline zinc oxide films may be significantly increased by >1019cm−3 by brief exposures to hydrogen plasma at room temperature and decreased by exposure to O2 plasmas. Room-temperature oxygen plasma removes a fraction of the H at donor sites but both elevated temperatures (∼225°C) and O2 plasma were required to remove the rest. We demonstrate that combinations of O2 and H2 plasma treatments can be used to manipulate the carrier density in ZnO films. However, we also show the existence of significant drifts (∼15%) in the carrier concentrations over very long time scales (hours). Possible sites for H incorporation in polycrystalline films and reasons for the observed carrier-concentration changes are proposed.
Modeling of and experiments on dust particle levitation in the sheath of a radio frequency plasma reactor
Authors: Setyawan Heru , Shimada Manabu , Hayashi Yutaka , Okuyama Kikuo , Winardi Sugeng
Published: January 2005

The equilibrium and trapping of dust particles in a plasma sheath are investigated, both experimentally and theoretically. A self-consistent sheath model including input power as one of the model parameters is proposed, to predict the equilibrium position of particle trap. The electron temperature and density are estimated from the observed current and power (I-P) characteristics using the sheath model developed. Direct comparisons are made between the measured equilibrium position and the predicted equilibrium position. The equilibrium position moves closer to the electrode with increasing rf power and particle size. The position is apparently related to the sheath thickness, which decreases with increasing rf power. The model can correctly predict the experimentally observed trend in the equilibrium position of particle trap. It is found that the particle charge becomes positive when the particle gets closer to the electrode, due to the dominant influence of ion currents to the particle surface.
Morphological and magnetic properties of carbon–nickel nanocomposite thin films
Authors: Fonseca F. C. , Ferlauto A. S. , Alvarez F. , Goya G. F. , Jardim R. F.
Published: January 2005

Carbon–nickel nanocomposite thin films were prepared by ion beam cosputtering a graphite target having a nickel chip attached to its surface. The amount of Ni incorporated in the films was controlled by the size of the Ni chip (from 5to22wt%), and measured by in situ x-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy images indicated that the films have a granular structure with nanosize Ni particles embedded in an amorphous carbon matrix. The Ni particles have an average radius of ∼2nm, with a rather narrow size distribution. Magnetization measurements revealed that films are superparamagnetic and present blocking temperatures TB<13K. The combined results of XPS and magnetic measurements indicate that Ni particles are free from oxide layers. In addition, the estimated value of their anisotropy constant was found to be higher than the expected value for bulk Ni. The origin of this discrepancy is associated with both shape and interaction anisotropies.
Low-temperature growth and field emission of ZnO nanowire arrays
Authors: Cui J. B. , Daghlian C. P. , Gibson U. J. , Püsche R. , Geithner P. , Ley L.
Published: January 2005

Structural, optical, and field-emission properties of ZnO nanowire arrays grown at 90°C are investigated. Single-crystalline ZnO nanowires with low level of oxygen vacancies are obtained at low temperatures. The nanowire growth is strongly dependent on the seeding method used but independent of the substrate materials, which enable large scale growth of ZnO arrays on all kinds of substrates including polymers. We have demonstrated stable electron emission at low-field strengths for nanowires grown on polystyrene and polyethylene foils, making them promising candidates for fabrication of flexible cold cathodes. Deposition of a few nanometers of gold on ZnO nanowires significantly lowers the field required for electron emission, which is explained in terms of additional field enhancement from Au islands on top of the ZnO nanowires.
On Food Companies Liability for Obesity
Authors: Coestier Bénédicte , Gozlan Estelle , Marette Stéphan
Published: January 2005

The U.S. food industry faces tobacco‐style lawsuits for providing misleading information about health risks linked to the consumption of fatty products. This article investigates the link between alternative liability rules and the incentive for disclosing health information to consumers. We show that if the expected damage is relatively low, the absence of intervention is socially optimal. If the expected damage is not too high, mandatory labeling is socially optimal. Liability rules are only welfare‐enhancing for high levels of risk and/or when consumers misperceive health warnings.
The Harvesting Decisions When a Standing Forest with Multiple Age‐Classes Has Value
Authors: Uusivuori Jussi , Kuuluvainen Jari
Published: January 2005

A solution is demonstrated to an infinite‐horizon, discrete‐time utility model describing the consumption and cutting behavior of a nonindustrial private landowner who is managing a multiple age‐class forest and who values both consumption derived from harvesting the trees and amenity derived from the standing trees. A policy rule is derived to attain a normal forest from any initial age‐class distribution. It is demonstrated that a noncyclical forest allowing a constant periodic harvest is typically not a normal forest. Therefore, an even‐flow timber harvesting is not tied to the existence of a normal forest structure.
Modeling Discrete Choice with Uncertain Data: An Augmented MNL Estimator
Authors: Hellerstein Daniel
Published: January 2005

This article introduces a multinomial logit model that uses ancillary information to control for uncertainty in both the observed choices made by respondents, and in the attributes of a respondent's choice set. Simulated data are used to compare the performance of this estimator versus simpler models, under several different kinds of uncertainty.
Retail Price Fixity as a Facilitating Mechanism
Authors: Richards Timothy J. , Patterson Paul M.
Published: January 2005

Previous theoretical explanations for retail price fixity show that fixed retail prices can be consistent with either competitive or imperfectly competitive behavior. We develop a conceptual model of retail pricing wherein fixed price points are facilitating mechanisms for tacit collusion. A non‐cooperative equilibrium in fixed retail prices is supported through credible threats to revert to Nash pricing if cheating is suspected. We test the implications of this model using a two‐stage, ordered probit approach in weekly supermarket pricing data. The results show that price fixity does support collusive equilibria among retailers, but other factors may also explain retail price behavior.
The Persistence of Profitability among Firms in the Food Economy
Authors: Schumacher Sara K. , Boland Michael A.
Published: January 2005

The persistence of industry, firm‐specific, and corporate‐parent effects on firm profitability in the food economy are calculated and further analyzed within its four major sectors: food processing, wholesale grocery, retail supermarket, and restaurant. Profits are more persistent within an industry than within a corporation. The retail supermarket sector has had stable profits as has individual retail supermarket firms relative to the other three sectors.
Technological Change and Economies of Scale in U.S. Poultry Processing
Authors: Ollinger Michael , MacDonald James M. , Madison Milton
Published: January 2005

This article uses a unique data set provided by the Census Bureau and a translog cost function to empirically examine technological change in the U.S. poultry industry. Results reveal substantial scale economies that show no evidence of diminishing with plant size and that are much greater than those realized in cattle and hog slaughter. Findings suggest that consolidation is likely to continue, particularly if demand growth diminishes, and that controlling for plant product mix is critical to accurate cost estimates.
Economic Adjustments to Groundwater Depletion in the High Plains: Do Water‐Saving Irrigation Systems Save Water?
Authors: Peterson Jeffrey M. , Ding Ya
Published: January 2005

A common policy prescription for conserving irrigation water is to promote more efficient or “water‐saving” irrigation technologies. We develop a risk‐programing model to quantify the effect of irrigation efficiency on irrigation water use in the High Plains, taking account of irrigation timing and well capacity limits. We find that optimal irrigation does not respond monotonically to changes in efficiency, although intermediate and high‐efficiency systems both result in less water use than an inefficient flood system.
Farm Household Production Efficiency: Evidence from The Gambia
Authors: Chavas Jean‐Paul , Petrie Ragan , Roth Michael
Published: January 2005

This article investigates the economic efficiency of farm households, with an application to The Gambia. The efficiency analysis is conducted not at the farm level but at the household level, thus capturing the importance of off‐farm activities. Output‐based measures of technical, allocative, and scale efficiency are generated using nonparametric measurements. An econometric analysis of factors affecting the efficiency indexes is then conducted using a Tobit model. Technical efficiency is fairly high indicating that access to technology is not a severe constraint for most farm households. The cost of scale inefficiency is modest. Allocative inefficiency by contrast is found to be important for the majority of farm households. On the basis of the Tobit results, imperfections in markets for financial capital and nonfarm employment contribute to significant allocative inefficiency.
Credit Risk Models and Agricultural Lending
Authors: Katchova Ani L. , Barry Peter J.
Published: January 2005

Credit risk models are developed and used to estimate capital requirements for agricultural lenders under the New Basel Capital Accord. The study uses credit value‐at‐risk methods to calculate probability of default, loss given default, and expected and unexpected losses. Two applied models, CreditMetrics and Moody's KMV, are estimated using farm financial data. The results show that the necessary capital for agricultural lenders under the New Basel Accord varies substantially depending on the riskiness and granularity of the portfolio.
Collective Reputation and Quality
Authors: Winfree Jason A. , McCluskey Jill J.
Published: January 2005

Firms who sell regional or specialty products often share a collective reputation based on aggregate quality. Collective reputation can be approached as a dynamic common property resource problem. We show that for an experience good without firm traceability, individual firms have the incentive to choose quality levels that are sub‐optimal for the group. These results support minimum quality standards. Trigger strategies are analyzed as an alternative solution to this problem. Finally, the implications of these results are discussed as they relate to the case study of Washington apples.
Milk by Any Other Name … Consumer Benefits from Labeled Milk
Authors: Dhar Tirtha , Foltz Jeremy D.
Published: January 2005

This article uses revealed preferences of consumers to study the consumer benefits from rBST‐free and organic labeled milk. The article specifies and estimates a quadratic AIDS demand system model for different milk types using U.S. supermarket scanner data. The introduction of rBST‐free and organic milk is used to estimate consumer benefits that are decomposed into two components, competitive and variety effects. Results show significant consumer benefits from organic milk and to a lesser extent from rBST‐free milk. Based on the findings, we explore implications for present U.S. labeling standards.
Viewpoint: Option prices, preferences, and state variables
Authors: Garcia René , Luger Richard , Renault Éric
Published: January 2005

Abstract.  This paper surveys recent developments in the theory of option pricing. The emphasis is on the interplay between option prices and investors’ impatience and their aversion to risk. The traditional view, steeped in the risk‐neutral approach to derivative pricing, has been that these preferences play no role in the determination of option prices. However, the usual lognormality assumption required to obtain preference‐free option pricing formulas is at odds with the empirical properties of financial assets. The lognormality assumption is easily reconcilable with those properties by the introduction of a latent state variable whose values can be interpreted as the states of the economy. The presence of a covariance risk with the state variable makes option prices depend explicitly on preferences. Generalized option pricing formulas, in which preferences matter, can explain several well‐known empirical biases associated with preference‐free models such as that of Black and Scholes (1973) and the stochastic volatility extensions of Hull and White (1987) and Heston (1993).
Pensions and fertility incentives
Authors: Fenge Robert , Meier Volker
Published: January 2005

Abstract.  This paper discusses the welfare implications of a pay‐as‐you‐go pension reform by introducing a child benefit in an endogenous fertility setting. In the model of a small open economy, higher fertility is associated with a reduction of lifetime labour supply. The optimum share of fertility‐related pensions is always below unity, but generally positive. The former is true, since individuals do not take into account the impact of their labour supply choice on the parent generation. It is demonstrated that child allowances are equivalent to fertility‐related pensions as instruments to achieve the optimum allocation. JEL classification: H23, H55, J13
A tale of two cities and a Giffen good
Authors: Garratt Rod
Published: January 2005

Abstract.  A scenario is provided in which a house in Eden Mills, Ontario, is a Giffen good. The conditions derived in the example apply to other indivisible goods as well. JEL classification: D11
Public capital, asymmetric information, and economic growth
Authors: Ho Wai‐Hong , Wang Yong
Published: January 2005

Abstract.  We investigate the provision of public capital in an endogenous growth model with asymmetric information. In a credit market with costly screening, we show that the equilibrium contracts are characterized by the self‐selection of borrowers. Through identifying an additional adverse effect of taxation on growth, we show that the optimal tax rate in our model is smaller than the output elasticity of public capital. Therefore, our analysis justifies a more conservative tax policy in the presence of asymmetric information. Furthermore, our model suggests a number of implications that appear to be well supported by preliminary evidence in cross‐country data. JEL classification: D82, H21, O41
Strategic union delegation and strike activity
Authors: Mauleon Ana , Vannetelbosch Vincent
Published: January 2005

Abstract.  We develop a model of wage determination with private information, in which the union has the option to delegate the wage bargaining to either surplus‐maximizing delegates or to wage‐maximizing delegates (such as senior union members). We show that the wage outcome in case of surplus‐maximizing delegates is not necessarily smaller than the wage outcome in case of wage‐maximizing delegates, even when the wage bargaining with private information is close to one with complete information. However, if it is commonly known that the union is stronger than the firm and the demand is sufficiently elastic, then delegating to wage‐maximizing delegates definitely increases the wage at equilibrium. The maximum delay in reaching an agreement is greater whenever the union chooses wage‐maximizing delegates instead of surplus‐maximizing delegates and remains finite even when the period length shrinks to zero. JEL classification: C70, C71, C72, C78
Ex post bidding and efficient coordination unemployment
Authors: Julien Benoît , Kennes John , King Ian
Published: January 2005

Abstract.  We study the implementation of constrained‐efficient allocations in labour markets where a basic coordination problem leads to an equilibrium matching friction. We argue that these allocations can be achieved in a non‐cooperative equilibrium if wages are determined by ex post bidding. This holds true even in finite‐sized markets where the equilibrium‐matching process has decreasing returns to scale – where the ‘Hosios rule’ does not apply – both with and without heterogeneity. JEL classification: D83, J64
Unemployment and the welfare effects of trade policy
Authors: Kreickemeier Udo
Published: January 2005

Abstract.  In this paper the welfare effects of tariffs and import quotas in the presence of involuntary unemployment are derived and compared. The framework used is the standard model of a competitive small open economy with many goods and factors. Optimum levels of the respective trade policy instruments are derived, as well as welfare increasing reform strategies. In all cases, the labour intensity of the import‐competing sectors turns out to be a crucial variable for deriving the welfare effects. JEL classification: F13, F16
Antidumping protection and R&D competition
Authors: Gao Xiwang , Miyagiwa Kaz
Published: January 2005

Abstract.  In recent years antidumping protection has spread throughout the world. Evidence shows that antidumping often targets R&D‐intensive sectors, raising a concern that it may adversely affect worldwide investments in R&D. We investigate this issue in a model of reciprocal dumping extended to a two‐stage game, in which two firms first choose R&D levels and then compete in prices. We find that, when a single government institutes antidumping law, the protected firm decreases investment in R&D, while the constrained firm invests more. When both governments engage in antidumping actions, both firms invest more in R&D than under free trade. JEL classification: F12, F13
Welfare‐ranking ad valorem and specific tariffs under monopolistic competition
Authors: Jørgensen Jan G. , Schröder Philipp J.H.
Published: January 2005

Abstract.  Actual trade and tariff policy prefers ad valorem tariffs to specific tariffs. Yet in this paper we show that, in a setting of monopolistic competition, realizing a given restriction on imports via a specific tariff would generate more consumer utility than obtaining the same restriction via an ad valorem tariff. JEL classification: F12
A factor endowment theory of international trade under imperfect competition and increasing returns
Authors: Fujiwara Kenji , Shimomura Koji
Published: January 2005

Abstract.  Constructing a two‐good (competitive and imperfectly‐competitive goods), two‐primary factor (capital and labor) and two‐country model of international trade where the imperfectly‐competitive sector is subject to increasing returns to scale, we establish an oligopolistic version of the Heckscher‐Ohlin theorem. JEL classification: F10, F12
Abstracts of the 23rd Annual Meeting of the Willi Hennig Society. “Phylogenetics and Evolutionary Biology”
Authors: Grandcolas Philippe
Published: January 2005

The 23rd annual meeting of the Willi Hennig Society took place in Paris with the support of Muséum national d'Histoire naturelle and CNRS (Centre National de la recherche Scientifique), from the 18th to the 23rd of July 2004. Ninety four participants from 16 countries presented 67 talks and 11 posters. The symposia comprised both methodological contributions and strong analyses of case studies, focusing on hot topics in systematics, methodological advances in phylogenetic analysis, epistemology, phylogenetic analysis of behavioral and ecological traits, phylogeny and coevolution of microbial symbioses, taxon and character sampling, biogeography, and the evolution of arthropods. The student participation was very high with 30 student talks (45%) distributed among all symposia, showing the same healthy trend seen in previous meetings. The present abstracts show how much systematics and phylogenetics are scientifically growing and contribute significantly to all research fields of evolutionary biology in the framework of comparative biology.

The Student Awards Committee (Cyrille D'Haese, Diana Lipscomb, John Wenzel) nominated the following winners: Johannes Bergsten, the Hennig Prize ($1000) for “Antagonistic coevolution between the sexes in diving‐beetles (Coleoptera: Dytiscidae); phylogeny and experiments in reciprocal illumination”, Mahé Ben Hamed, the Brundin Prize ($500) for “Reconstructing the history of Chinese through lexicon. Cladistics, distances and trees” and Lara Lopardo, the Rosen Prize ($250) for the poster “Chilean Anapids and Their Webs, a Phylogenetic Approach (Araneae, Anapidae)”.

© The Willi Hennig Society 2004.
Mapping characters on a tree with or without the outgroups
Authors: Grandcolas Philippe , Guilbert Eric , Robillard Tony , D'Haese Cyrille A. , Murienne Jérôme , Legendre Frédéric
Published: January 2005

A character of special interest in evolutionary studies is usually optimized on a phylogenetic tree, with or without the outgroups employed in that analysis. Both practices are never justified and look like arbitrary choices. Focusing on one example, we draw the conclusion that authors retain or remove outgroups depending on the way these outgroups sample the diversity of states of the character(s) of special interest. The topology without outgroups is often used by authors when different outgroup taxa non‐exhaustively sample the different states of the character of interest outside of the ingroup. This can make the analysis incoherent, because its different steps are not based on the same data matrix (outgroups are removed in the last step). It can provide several incoherent and possibly different patterns for a same character of interest, one issuing from the first step of phylogeny construction and the other resulting from the a posteriori optimization on the truncated topology. Phylogenetic analyses should be designed to minimize this problem, selecting outgroup and ingroup taxa whose diversity of character states is needed for reconstructing the evolutionary history of the character of interest. © The Willi Hennig Society 2004.
Mitochondrial genome data alone are not enough to unambiguously resolve the relationships of Entognatha, Insecta and Crustacea sensu lato (Arthropoda)
Authors: Cameron Stephen L. , Miller Kelly B. , D'Haese Cyrille A. , Whiting Michael F. , Barker Stephen C.
Published: January 2005

An analysis of the relationships of the major arthropod groups was undertaken using mitochondrial genome data to examine the hypotheses that Hexapoda is polyphyletic and that Collembola is more closely related to branchiopod crustaceans than insects. We sought to examine the sensitivity of this relationship to outgroup choice, data treatment, gene choice and optimality criteria used in the phylogenetic analysis of mitochondrial genome data. Additionally we sequenced the mitochondrial genome of an archaeognathan, Nesomachilis australica, to improve taxon selection in the apterygote insects, a group poorly represented in previous mitochondrial phylogenies. The sister group of the Collembola was rarely resolved in our analyses with a significant level of support. The use of different outgroups (myriapods, nematodes, or annelids + mollusks) resulted in many different placements of Collembola. The way in which the dataset was coded for analysis (DNA, DNA with the exclusion of third codon position and as amino acids) also had marked affects on tree topology. We found that nodal support was spread evenly throughout the 13 mitochondrial genes and the exclusion of genes resulted in significantly less resolution in the inferred trees. Optimality criteria had a much lesser effect on topology than the preceding factors; parsimony and Bayesian trees for a given data set and treatment were quite similar. We therefore conclude that the relationships of the extant arthropod groups as inferred by mitochondrial genomes are highly vulnerable to outgroup choice, data treatment and gene choice, and no consistent alternative hypothesis of Collembola's relationships is supported. Pending the resolution of these identified problems with the application of mitogenomic data to basal arthropod relationships, it is difficult to justify the rejection of hexapod monophyly, which is well supported on morphological grounds.

© The Willi Hennig Society 2004.
The phylogenetic position of the comb jellies (Ctenophora) and the importance of taxonomic sampling
Authors: Wallberg Andreas , Thollesson Mikael , Farris James S. , Jondelius Ulf
Published: January 2005

The transition to a vermiform body shape is one of the most important events in animal evolution, having led to the impressive radiation of Bilateria. However, the sister group of Bilateria has remained obscure. Cladistic analyses of morphology indicate that Ctenophora is the sister group of Bilateria. Previous analyses of SSU rRNA sequences have yielded conflicting results; in many studies Ctenophora forms the sister group of Cnidaria + Bilateria, but in others the ctenophores group with poriferans. Here we re‐examine the SSU sequence by analyzing a dataset with 528 metazoan + outgroup sequences, including almost 120 poriferan and diploblast sequences. We use parsimony ratchet and jackknife methods, as well as Bayesian methods, to analyze the data. The results indicate strong phylogenetic signals for a cnidarian + bilaterian group and for the comb jellies to have branched off early within a group uniting all epithelial animals [(Ct,(Cn,Bi))]. We demonstrate the importance of inclusive taxonomic coverage of ribosomal sequences for resolving this problematic part of the metazoan tree: topological stability increases dramatically with the addition of taxa, and the jackknife frequencies of the internal nodes uniting the lineages [(Cn,Bi) and ((Ct,(Cn,Bi))] also increase. We consider the reconstructed topology to represent the current best hypothesis of the interrelationships of these old lineages. Some morphological features supporting alternative hypotheses are discussed in the light of this result.

© The Willi Hennig Society 2004.