bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of H2 dissociation dynamics on the Pd(111) surface
Authors: Crespos C. , Busnengo H. F. , Dong W. , Salin A.
Published: March 2003

We perform a detailed analysis of the dynamics of the dissociative adsorption of H2 molecules on a Pd(111) surface using ab initio data for the molecule–surface interaction and classical trajectory methods. We show that the reaction probability is completely determined by the molecule–surface interaction in the approach toward the surface before it reaches a critical distance of 1.5 Å. The corresponding dynamics can be reduced to a 2D one, involving only the translational and rotational degrees of freedom, except in the lower energy range where an important role is played by dynamic trapping. We establish the relation between the dissociation probability and the shape of 2D cuts of the potential energy surface using a simple model of the evolution of orientational forces as the molecule approaches the surface. Whereas above 1.5 Å the molecule evolves “as a whole,” below 1.5 Å the dynamics has the character of independent atom–surface interactions which explains why it dissociates with a probability close to one once it has reached the critical distance of 1.5 Å.
A Drude-model approach to dispersion interactions in dipole-bound anions
Authors: Wang F. , Jordan K. D.
Published: March 2003

A one-electron model potential for calculating the binding energy of an excess electron interacting with polar molecules and their clusters is described. The unique feature of this potential is the treatment of polarization and dispersion effects by means of a Drude model. The approach is tested by calculating the energies for binding an excess electron to HCN, (HCN)2, HNC, and (HNC)2. The model potential results are found to be in good agreement with the predictions of high-level all-electron calculations.
Investigation of collisional quenching of CCl2 (Ã 1B1 and ã 3B1) by alkanes
Authors: Gao Yide , Pei Linsen , Chen Yang , Chen Congxiang
Published: March 2003

CCl 2 free radicals were produced by a pulsed dc discharge of CCl4 (in Ar). Ground electronic state CCl2(X̃) radical was electronically excited to Ã 1B1(0,4,0) vibronic state by Nd:YAG laser pumped dye laser at 541.52 nm. The laser induced fluorescence signal is observed to be a monoexponential decay curve corresponding to the decay of the Ã state under supersonic jet conditions and the lifetime of CCl2(Ã→X̃) transition was measured being 0.83±0.03 μs. Experimental quenching data of excited CCl2(Ã 1B1 and ã 3B1) by alkanes were obtained by observing the time-resolved total fluorescence signal of the excited CCl2 radical in a cell, which showed a superposition of two exponential components under the presence of a quencher. The quenching rate constants of Ã(1B1) and ã(3B1) states of CCl2, KA, and Ka, were derived by analyzing the experimental data according to a proposed three-level model to deal with the CCl2(X̃ 1A1,Ã 1B1,ã 3B1) system. KA and Ka increase steadily by increasing the number of C–H bonds contained in the alkane molecules. The formation cross sections of the complexes of electronically excited CCl2 radicals and alkane molecules were calculated by means of a collision complex model. It is shown that the dependence of the formation cross section of the complex on the number of C–H bonds contained in the alkane molecule is in agreement with that of the measured quenching cross section.
Ã
2
Π
u
state-intermediated two-photon dissociation of CS2+ via the first channel
Authors: Zhang Limin , Chen Jun , Xu Haifeng , Dai Jinghua , Liu Shilin , Ma Xingxiao
Published: March 2003

The [1+1] Ã 2Πu-state resonance enhanced two-photon dissociation process of CS2+ molecular ions has been investigated by measuring the photofragment S+ excitation (PHOFEX) spectrum in the wavelength range of 424–482 nm, where the CS2+ molecular ions were prepared purely by [3+1] multiphoton ionization of the neutral CS2 molecules at 483.2 nm. The PHOFEX spectrum was assigned essentially to the CS2+(Ã 2Πu)←CS2+(X̃ 2Πg) transition, and the dissociation mechanism of CS2+ was preliminarily attributed to (i) CS2+(X̃ 2Πg)→CS2+(Ã 2Πu) through one-photon excitation, (ii) CS2+(Ã 2Πu)→CS2+(X̃†) via internal conversion process due to the vibronic coupling between the Ã and X̃ states, (iii) CS2+(X̃†)→CS2+(B̃ 2Σu+) through the second photon excitation, and (iv) CS2+(B̃ 2Σu+)→S++CS owing to the potential curve crossing with the repulsive Σ−4 state correlated with the first dissociation limit.
A restricted dimensionality quasiclassical trajectory study of H2(v,0)+H2(v′,0)
Authors: Mandy M. E. , Rothwell T. A. , Martin P. G.
Published: March 2003

Quasiclassical trajectory calculations for H2(v,0)+H2(v′,0) have been carried out for collisional energies up to 350 mEh in selected geometries to elucidate the dynamical effects of various features in the potential-energy surface. The chemically accurate potential fitted by Keogh (Ph.D. Thesis, Toronto, 1992) to the ab initio points of Boothroyd et al. [J. Chem. Phys. 95, 4331 1991] was used. Geometries considered include isosceles trapezoidal, isosceles tetrahedral, and “T” conformations. For each geometry, representative trajectories are considered and the energy range is sufficient to determine and characterize the probabilities of elastic, inelastic, singly dissociative, and doubly dissociative outcomes. Also determined are the probability of exchange for the isosceles trapezoidal geometry and the probability of three body outcomes for the “T” geometry. The results are discussed in terms of the interaction potential.
Chirp reduction in semiconductor lasers through injection current patterning
Authors: Dokhane N. , Lippi G. L.
Published: March 2003

The introduction of patterned current fronts that modulate the transition between directly modulated optical bits allows for a strong reduction of the optical chirp in a single-mode semiconductor laser, as shown in the numerical integration of a standard model. Hence, optical transmission of information over much longer distances without signal deterioration and a substantial increase in data transmission speed are possible.
Broadening the potential bandwidth of piezoelectric transducers by partial depolarization
Authors: Hariti Sid Ahmed , Holé Stéphane , Lewiner Jacques
Published: March 2003

Elastic waves are used more and more in a nondestructive way to probe the physical properties of materials. The resolution of the images or the accuracy of the measurements is directly associated with the ultrasonic signal bandwidth and amplitude a system can generate or detect. The authors propose a technique to broaden the potential bandwidth of piezoelectric generators and sensors, which is based on utilizing a nonuniformly-polarized piezoelectric material. Both simulated and experimental responses are shown. They are in good agreement and exhibit a useful bandwidth over several natural harmonics of the piezoelectric transducer.
Modeling and characterization of direct tunneling hole current through ultrathin gate oxide in p-metal–oxide–semiconductor field-effect transistors
Authors: Hou Y. T. , Li M. F. , Lai W. H. , Jin Y.
Published: March 2003

We report the calculation of hole direct tunneling (DT) current from the inversion layer in a p-metal–oxide–semiconductor field-effect transistor based on a solid physical background. Our results are in good agreement with those obtained from carrier separation measurements over a wide range of oxide thicknesses in the ultrathin regime. The effect of valence band mixing on hole quantization in an inversion layer in a Si substrate is properly accounted for by an improved one-band effective mass approximation. A modified Wentzel–Kramers–Brillouin approximation to calculate the hole transmission probability is used by adopting a more accurate dispersion equation in the oxide gap. Our method is general, simple, and computationally efficient. It may even be used to calculate the hole DT current in other gate dielectric materials.
Effect of growth stoichiometry on the electrical activity of screw dislocations in GaN films grown by molecular-beam epitaxy
Authors: Hsu J. W. P. , Manfra M. J. , Chu S. N. G. , Chen C. H. , Pfeiffer L. N. , Molnar R. J.
Published: March 2003

The impact of the Ga/N ratio on the structure and electrical activity of threading dislocations in GaN films grown by molecular-beam epitaxy is reported. Electrical measurements performed on samples grown under Ga-rich conditions show three orders of magnitude higher reverse bias leakage compared with those grown under Ga-lean conditions. Transmission electron microscopy (TEM) studies reveal excess Ga at the surface termination of pure screw dislocations accompanied by a change in the screw dislocation core structure in Ga-rich films. The correlation of transport and TEM results indicates that dislocation electrical activity depends sensitively on dislocation type and growth stoichiometry.
Coulomb glass origin of defect-induced dielectric loss in thin-film oxides
Authors: Fleming R. M. , Varma C. M. , Lang D. V. , Jones C. D. W. , Steigerwald M. L. , Kowach G. R.
Published: March 2003

The dielectric loss in amorphous, thin-film oxide insulators produces a real part of the ac conductivity σ′(ω) that scales as ωs with s∼1. Conventional models explain this frequency dependence by hopping or tunneling of charge between neighboring defect sites. These models fail at low temperatures since they predict that σ′ should vanish at T=0. We observe that the ac conductivity of Ta2O5, ZnO, and SiO2 has a nonzero extrapolated value at T=0. We propose that this behavior is consistent with the predictions of a Coulomb glass, an insulator with a random distribution of charged defects.
Cavity-quantum electrodynamics using a single InAs quantum dot in a microdisk structure
Authors: Kiraz A. , Michler P. , Becher C. , Gayral B. , Imamoğlu A. , Zhang Lidong , Hu E. , Schoenfeld W. V. , Petroff P. M.
Published: March 2003

We investigate cavity-quantum electrodynamics (QED) effects in an all-semiconductor nanostructure by tuning a single self-assembled InAs quantum dot (QD) into resonance with a high quality factor microdisk whispering gallery mode (WGM). The stronger temperature dependence of the QD single-exciton (1X) resonance allows us to change the relative energy of the WGM and the 1X transitions by varying the sample temperature. The two coupled resonances exhibit crossing behavior due to the weak coupling cavity-QED regime. We demonstrate exciton lifetime reduction by 6 due to the Purcell effect by tuning the QD into resonance with the WGM. Our experiments also show that single-exciton lifetime is independent of temperature up to 50 K.
Optical transitions and excitonic recombination in InAs/InP self-assembled quantum wires
Authors: Alén Benito , Martı́nez-Pastor Juan , Garcı́a-Cristobal Alberto , González Luisa , Garcı́a Jorge M.
Published: March 2003

InAs self-assembled quantum wire structures have been grown on InP substrates and studied by means of photoluminescence and polarized-light absorption measurements. According to our calculations, the observed optical transitions in each sample are consistent with wires of different heights, namely from 6 to 13 monolayers. The nonradiative mechanism limiting the emission intensity at room temperature is related to thermal escape of carriers out of the wires.
Nonlinear-optic and ferroelectric behavior of lithium borate–strontium bismuth tantalate glass–ceramic composite
Authors: Senthil Murugan G. , Varma K. B. R. , Takahashi Yoshihiro , Komatsu Takayuki
Published: March 2003

Transparent glasses in the system (100–x) Li2B4O7–xSrBi2Ta2O9 (0⩽x⩽20) were fabricated via a splat-quenching technique. The glassy nature of the as-quenched samples was established by differential thermal analyses. X-ray powder diffraction and transmission electron microscopic studies confirmed the amorphous nature of the as-quenched and crystallinity (40 nm) in the heat-treated (glass–ceramic) samples. The dielectric constant (εr) of the glass–ceramic composite (x=20, heat treated at 773 K/8 h) was in between that of the parent host glass (Li2B4O7) and strontium bismuth tantalate ceramics in the frequency range 100 Hz–40 MHz at 300 K. These exhibited intense second-harmonic generation and a ferroelectric hysteritic behavior (P vs E loops) at 300 K. The coercive field (Ec) and the remnant polarization (Pr) were 1053 V/cm and 0.483 μC/cm2, respectively.
Structural properties of a GaNxP1−x alloy: Raman studies
Authors: Buyanova I. A. , Chen W. M. , Goldys E. M. , Xin H. P. , Tu C. W.
Published: March 2003

Raman measurements in backscattering configuration are employed to characterize the effect of nitrogen on the structural properties of a GaNxP1−x alloy with x⩽3%. The following effects of N incorporation on the vibrational spectra of GaNP are observed. First, frequencies of GaP-like and GaN-like longitudinal optical phonons exhibit strong compositional dependence, due to a combined effect of alloying and biaxial strain. Second, a dramatic quenching of two-phonon Raman scattering and an emergence of zone-edge GaP-like vibrations are observed. These effects are tentatively attributed to a local distortion of the GaNP lattice and/or compositional disorder in the alloy.
Imaging of trapped charge in SiO2 and at the SiO2–Si interface
Authors: Ludeke R. , Cartier E.
Published: March 2003

Charged defects in SiO2 and at the SiO2–Si(111) interface were imaged with a noncontact atomic force microscope. Electrons and holes trapped at interfacial Pb centers in n- and p-type samples were identified from simultaneously recorded Kelvin images. Limited trap occupancy, determined by the local, bias controlled Fermi level, and strong band bending lead to unusually sharp images of trapped charge.
Direct measurement of sub-10 nm-level lateral distribution in tunneling-electron luminescence intensity on a cross-sectional 50-nm-thick AlAs layer by using a conductive transparent tip
Authors: Murashita Tooru , Tateno Kouta
Published: March 2003

Tunneling-electron luminescence (TL) from nanometer-sized regions can be effectively collected with a conductive transparent (CT) tip that injects tunneling electrons and simultaneously collects luminescence. By using the CT tip, the lateral distribution of TL intensities has been directly measured on a cleaved 50-nm-thick AlAs layer in AlAs/GaAs multiple quantum wells. The TL intensity distribution measured on the AlAs layer agree fairly well with the sum of the exponential decay functions from each GaAs/AlAs interface with a decay length of 8 nm with an accuracy as high as a one-pixel interval of 3 nm. This decay length is close to the thermalization length of tunneling electrons in the AlAs layer.
Thermodynamic regulation of actin polymerization
Authors: Niranjan Priya S. , Forbes Jeffrey G. , Greer Sandra C. , Dudowicz Jacek , Freed Karl F. , Douglas Jack F.
Published: March 2003

A Flory–Huggins-type lattice model of actin polymerization under equilibrium conditions is employed to analyze new spectroscopic measurements for the extent of actin polymerization Φ as a function of temperature T, salt concentration [KCl], and the initial concentration of actin monomers [G0]. The theory subsumes existing mechanisms for actin monomer initiation, dimerization, and chain propagation. The extent of polymerization Φ increases with T to an unanticipated maximum, and the calculations explain this unusual effect as arising from a competition between monomer activation, which diminishes upon heating, and propagating chain growth, which increases upon heating. The actin polymerization is described as a rounded phase transition, and the associated polymerization temperature Tp depends strongly, but nearly linearly on [G0] and [KCl] over the concentration regimes investigated. Our findings support the suggestion that physicochemical changes can complement regulatory proteins in controlling actin polymerization in living systems.
Theory of lithographically-induced self-assembly
Authors: Suo Z. , Liang J.
Published: March 2003

Recent experiments show that, when a two-phase fluid confined between parallel substrates is subject to an electric field, one phase can self-assemble into a triangular lattice of islands in another phase. We describe a theory of the stability of the island lattice. It is well known that the total interface energy reduces when the island diameter increases. We show that, under certain conditions, the electrostatic free energy reduces when the island diameter decreases. The islands select the equilibrium diameter to minimize the combined interface energy and electrostatic energy. We describe the conditions for electrostatic field to stabilize the island lattice, and analyze an idealized model. The theory suggests considerable experimental control over stable island size.
Magnetooptical spectroscopy of magnetic multilayers: Theory and experiment (A review)
Authors: Antonov V. N. , Uba L. , Uba S. , Yaresko A. N. , Perlov A. Ya. , Nemoshkalenko V. V.
Published: March 2003

Experimental and theoretical results on the optical and magnetooptical (MO) spectral properties of a series of Co/Cu, Co/Pd, Co/Pt and Fe/Au multilayers are reviewed. Diagonal and off-diagonal components of the optical conductivity tensor have been determined in the photon energy range 0.8-5.5 eV from the polar and longitudinal Kerr rotation as well as ellipticity and ellipsometry measurements. The conductivity tensor has been evaluated on the basis of self-consistent spin-polarized relativistic linear muffin-tin orbital (LMTO) band-structure calculations within the local spin-density approximation. The role of the spin polarization and the spin–orbit interaction in the formation of the magnetooptical Kerr effect (MOKE) spectra as inferred from first-principles calculations is examined and discussed. The high sensitivity of the MO properties to the interface structure is studied by ab initio modeling of the effects of the interfacial alloying, substitutional disorder, and the roughness at the interfaces. It is shown that the MOKE spectra of the multilayered structures (MLS) calculated using the LMTO method reproduce the experimental spectra only moderately well if ideal MLS with sharp interfaces are assumed. It is shown that the MOKE spectra of the MLS can be adequately reproduced only by taking into account their real interface microstructure. The magnetooptical anisotropy (MOA) is studied both experimentally and theoretically for a series of Fen/Aun superlattices prepared by molecular beam epitaxy with n=1,2,3 Fe and Au atomic planes of (001) orientation. The results of the LMTO calculations show that the microscopic origin of the large MOA is the interplay of the strong spin-orbit coupling on Au sites and the large exchange splitting on Fe sites via Aud–Fe d hybridization of the electronic states at the interfaces. The orientation anisotropy of the d orbital moment is calculated from first principles and analyzed on the basis of d orbital symmetry considerations. The relationship between the orbital moment anisotropy and the MOA is discussed. The reviewed results imply that the magnetooptical properties of multilayers with various compositions and structures can be quantitatively predicted from first-principles band-structure calculations. Such a possibility is important for basic research as well as applications.
Features of the magnetoelectric properties of BiFeO3 in high magnetic fields
Authors: Popov Yu. F. , Kadomtseva A. M. , Krotov S. S. , Belov D. V. , Vorob’ev G. P. , Makhov P. N. , Zvezdin A. K.
Published: March 2003

It is shown that the destruction of the cycloidal structure of the magnetic ferroelectric BiFeO3 by a high magnetic field (Hn≈200 kOe) leads to the onset of a linear magnetoelectric effect and the appearance of a toroidal moment. The proof of the existence of a toroidal moment T in a high magnetic field (H>Hn) is based on the experimental observation that the off-diagonal components of the linear ME effect tensor are asymmetric (α12=−α21 for L‖c, where L is the antiferromagnetic vector), inasmuch as Tz∼α12−α21.
Magnetoelectric resonance of phonon and magnon polaritons in a ferrimagnet
Authors: Chupis I. E. , Mishchenko A. A.
Published: March 2003

The influence of the dynamic magnetoelectric interaction on the magnon (TE) and phonon (TM) polaritons in a ferrimagnet is studied in the IR region of the spectrum. The frequency dispersion of the dielectric permittivity and magnetic permeability is taken into account. It is shown that the spontaneous magnetic moment induces an additional radiative mode in the spectrum of TM polaritons. It is predicted that a resonant interaction and interconversion of the TM and TE polaritons can occur in a static electric field.
Phonon echo in hydrogen-containing metals
Authors: Chotorlishvili L. L. , Tutberidze I. A. , Kakabadze G. R.
Published: March 2003

The phonon echo due to the tunneling of the hydrogen atom between two equilibrium positions in hydrogen-containing niobium NbOxHy is investigated. The time dependence of the intensity and shape of the two-pulse echo signal is obtained.
The C-terminal Extension of a Hybrid Immunoglobulin A/G Heavy Chain Is Responsible for Its Golgi-mediated Sorting to the Vacuole
Authors: Hadlington Jane L. , Santoro Aniello , Nuttall James , Denecke Jürgen , Ma Julian K-C. , Vitale Alessandro , Frigerio Lorenzo
Published: March 2003

We have assessed the ability of the plant secretory pathway to handle the expression of complex heterologous proteins by investigating the fate of a hybrid immunoglobulin A/G in tobacco cells. Although plant cells can express large amounts of the antibody, a relevant proportion is normally lost to vacuolar sorting and degradation. Here we show that the synthesis of high amounts of IgA/G does not impose stress on the plant secretory pathway. Plant cells can assemble antibody chains with high efficiency and vacuolar transport occurs only after the assembled immunoglobulins have traveled through the Golgi complex. We prove that vacuolar delivery of IgA/G depends on the presence of a cryptic sorting signal in the tailpiece of the IgA/G heavy chain. We also show that unassembled light chains are efficiently secreted as monomers by the plant secretory pathway.
The RAG1 N-terminal domain is an E3 ubiquitin ligase
Authors: Yurchenko Vyacheslav , Xue Zhu , Sadofsky Moshe
Published: March 2003

RAG1 and RAG2 initiate V(D)J recombination, which is the assembly of immunoglobulin and T cell receptor genes. The N-terminal region of RAG1 can be deleted, leaving an enzymatic “core” able to catalyze the complete reaction. Here we report that the N-terminal portion of RAG1 has a distinct enzymatic role separate from the rest of the protein. It acts as an E3 ligase in the ubiquitylation of a test substrate and formation of polyubiquitin chains in vitro. This finding suggests a new way in which V(D)J recombination can be regulated and coupled to other aspects of cell physiology.
Enhancer–promoter communication mediated by Chip during Pannier-driven proneural patterning is regulated by Osa
Authors: Heitzler Pascal , Vanolst Luc , Biryukova Inna , Ramain Philippe
Published: March 2003

The GATA factor Pannier activates proneuralachaete/scute(ac/sc) expression during development of the sensory organs ofDrosophilathrough enhancer binding. Chip bridges Pannier with the (Ac/Sc)–Daughterless heterodimers bound to the promoter and facilitates the enhancer–promoter communication required for proneural development. We show here that this communication is regulated by Osa, which is recruited by Pannier and Chip. Osa belongs to Brahma chromatin remodeling complexes and we show that Osa negatively regulatesac/sc. Consequently, Pannier and Chip also play an essential role during repression of proneural gene expression. Our study suggests that altering chromatin structure is essential for regulation of enhancer–promoter communication.
Stop‐and‐Go Agricultural Policies
Authors: Bourgeon Jean‐Marc , Chambers Robert G.
Published: March 2003

The optimal design of farm policy and public investment in agriculture in the presence of asymmetric information between the government and farmers is studied. It is shown that a mix of capped deficiency payments and voluntary paid land diversion can implement the optimal policy outcome. Optimal program design requires large farmers to farm all their land, and small farmers may or may not divert acreage. Decoupled policies are never optimal.
The Goals of U.S. Agricultural Policy: A Mechanism Design Approach
Authors: Hueth Brent
Published: March 2003

This article examines motivations underlying the government's choice of alternative policy mechanisms for subsidizing agriculture. Optimal policies are analyzed for three government objectives: one where the government wishes to ensure a minimum level of net income for all farmers, a second where the government's only concern is to transfer income from consumers and taxpayers to the farm sector, and a final “augmented” income‐transfer objective. The analysis offers an explanation for agricultural policy mechanisms that involve overproduction by high‐cost producers, relative to a free‐market equilibrium. Such a distortion might arise from the existence of nonmarket values for the production of relatively high‐cost farmers in the government's objective.
Information Value and Risk Premium in Agricultural Production: The Case of Split Nitrogen Application for Corn
Authors: Bontems Philippe , Thomas Alban
Published: March 2003

This article considers an agricultural production model of sequential nitrogen application under risk. Because of random shocks between subsequent production stages, optimal fertilization decisions depend on the magnitude of farmers' risk aversion (risk premium), and the possibility for farmers to process information (value of information). We propose a joint estimation procedure of technology and risk aversion parameters, using a structural, simulation‐based econometric procedure. Parameter estimates allow to compute both the value of information and the risk premium, which account for about 30% of fertilizer cost for Midwest corn producers.
Valuation of Credit Risk in Agricultural Mortgages
Authors: Sherrick Bruce J. , Barry Peter J. , Ellinger Paul N.
Published: March 2003

A credit‐risk valuation model is developed and empirically implemented to estimate the cost of insuring against credit risks in pools of agricultural mortgage loans. Probabilistic information about loss distributions across a broad set of loan‐level and pool‐level characteristics is used to assess insurance valuation and solvency likelihood. The effects on the value of credit‐risk insurance of pool size, deductibles, timing alterations, premium loadings, adverse loan selection, and changing underwriting standards are also estimated. Results indicate that actuarial insurance costs are initially highly sensitive and then become relatively insensitive as pool size increases.
Estimating the Demand for a New Technology: Bt Cotton and Insecticide Policies
Authors: Hubbell Bryan J. , Marra Michele C. , Carlson Gerald A.
Published: March 2003

This article examines the potential demand for Bt cotton in the Southeast from information gathered in the first year of commercialization. We combine revealed preference (RP) data on adoption of Bt cotton varieties with stated preference (SP) data on willingness to adopt to estimate demand using a double‐bounded maximum likelihood procedure. Using estimated demand equations, we simulate the costs of reducing conventional insecticide applications through subsidization of Bt cotton. Results indicate that reducing cotton insecticide applications by 40% in the Southeast would require a $@@‐@@21/acre subsidy, with total annual program costs between $@@‐@@53 million and $@@‐@@60 million.
Timber Price Dynamics Following a Natural Catastrophe
Authors: Prestemon Jeffrey P. , Holmes Thomas P.
Published: March 2003

Catastrophic shocks to existing stocks of a renewable resource can cause long‐run price shifts. With timber, these long‐run price shifts may be accompanied by a short‐run price drop due to salvage. Hurricane Hugo damaged 20% of southern pine timber in the South Carolina Coastal Plain in 1989. To estimate the short‐ and long‐run effects of the hurricane on the prices of timber stocks, we estimated an intervention model of the residuals of cointegration of South Carolina sawtimber and pulpwood stumpage prices with prices of similar products from other regions. Modeling revealed a 30% negative price spike due to salvage and a long‐run enhancement effect, leading to prices that are 10% to 30% higher than they would have been had Hugo not occurred.
The Monthly Food Stamp Cycle: Shopping Frequency and Food Intake Decisions in an Endogenous Switching Regression Framework
Authors: Wilde Parke E. , Ranney Christine K.
Published: March 2003

Mean food spending by food stamp households peaks sharply in the first three days after benefits are received. For those who conduct major grocery shopping trips only once per month (42% of all food stamp households), mean food energy intake drops significantly by the fourth week of the month. For the remaining households, intake remains steady over the course of the month. These patterns motivate an empirical model that simultaneously accounts for the shopping frequency and food intake decisions over time. Results have implications for policies that may affect the frequency of grocery shopping by food stamp households.
Transactions Costs and Agricultural Household Supply Response
Authors: Key Nigel , Sadoulet Elisabeth , Janvry Alain De
Published: March 2003

We develop and estimate a model of supply response when transactions costs create a situation where some producers buy, others sell, and others do not participate in markets. We present two rationales for why producing households may have different relationships to the market: proportional and fixed transactions costs. Using data on Mexican corn producers, we estimate an empirical model that allows for separate tests of the significance of both types of transactions costs, revealing that both fixed and proportional transactions costs matter for the estimation. The results provide consistent estimates of supply elasticity and measures of the relative importance of factors determining both proportional and fixed transactions costs.
The Returns from Schooling in a Diversified Rural Economy
Authors: Taylor J. Edward , Yunez‐Naude Antonio
Published: March 2003

Controlling for the endogeneity of activity choice and considering both household‐head and family schooling, we findevid ence of high returns from schooling in both crop andnoncrop activities. As schooling levels increase, the returns from schooling shift away from crop production. Failure to control for activity selection andfamily schooling is likely to result in biasedestimates of the returns from schooling in individual activities.
A Test of Nutritional Quality Signaling in Food Markets Prior to Implementation of Mandatory Labeling
Authors: Mojduszka Eliza M. , Caswell Julie A.
Published: March 2003

In May 1994, new nutrition labeling regulations went into effect in the United States requiring mandatory disclosure of information on the nutritional content of foods. This article uses Grossman's model of totally effective quality signaling to evaluate whether markets were effective in information provision prior to the new regulation. If markets were effective in providing information to consumers on the nutritional quality of foods the new regulation would be unnecessary. The results of the logistic model, where the probability of voluntary information disclosure is linked to the nutritional quality of food products and their prices, indicate that private quality signaling was not reliably at work in food markets prior to implementation of the mandatory nutrition labeling regulation.
Valuing Water Supply Reliability
Authors: Griffin Ronald C. , Mjelde James W.
Published: March 2003

Instead of creating water supply systems that fully insulate mankind from climate‐imposed water deficiencies, it is possible that for municipal water systems a nonzero probability of water supply shortfall is efficient. Perfect water supply reliability, meaning no chance of future shortfall, is not optimal when water development costs are high. Designing an efficient strategy requires an assessment of consumer preferences pertaining to the reliability of water supply. Contingent valuations of both current and future shortfalls are reported. The consistency of these measures is gauged using an expected utility model.
Nonparametric and Semi‐Nonparametric Recreational Demand Analysis
Authors: Cooper Joseph C.
Published: March 2003

This paper addresses issues of specification testing for the travel cost method (TCM). Two nonparametric approaches to TCM analysis are presented. In addition, semi‐nonparametric count models for TCM are developed. A numerical illustration is provided in which the three methods are applied to an actual TCM data set on waterfowl hunting and the results are compared to those from a parametric analysis.
Nonparametric Estimation of Crop Insurance Rates Revisited
Authors: Ker Alan P. , Goodwin Barry K.
Published: March 2003

With the crop insurance program becoming the cornerstone of U.S. agricultural policy, recovering accurate rates is of paramount interest. Lack of yield data presents, by far, the most fundamental obstacle to recovery of accurate rates. This article employs new methodology to estimate conditional yield densities and derive the insurance rates. In our application, we find the nonparametric kernel density estimator requires an additional twenty‐six years of yield data to estimate the shape of the conditional yield densities as accurately as the recently developed empirical Bayes nonparametric kernel density estimator. Such methodological improvements can significantly aid in ameliorating the data problem.
Brand Choice and Purchase Frequency Revisited: An Application to Recreation Behavior
Authors: Shaw W. Douglas , Shonkwiler J. Scott
Published: March 2003

The role that total purchases play in determining the choice among brands has been considered in microeconomic theory for quite some time, but for traditional goods only. Consumption of outdoor recreation is an unusual good, most often measured using an individual's recreational trip. Adding the trips made on a number of choice occasions seems the obvious way to aggregate this good, but doing so leads to several problems in defining a meaningful price index. The Hicks‐Leontief conditions for aggregation suggest that trips to destinations may be thought of as brand choices on consumption occasions, andthe continuous analogue to total purchases may in fact be the individual's total travel. An empirical example of the model is used to estimate welfare impacts for a group of anglers.
The Economic Threshold with a Stochastic Pest Population: A Real Options Approach
Authors: Saphores Jean‐Daniel M.
Published: March 2003

Using real options,this paper formulates an optimal stopping model for applying pest control measures when the density of a pest population varies randomly. A delay between successive pesticide applications is introduced to analyze the farmer's expected marginal cost of reentry. This model is applied to the control of a foliar pest of apples via a pesticide, and is solved numerically. A sensitivity analysis shows that the pest density that should trigger pesticide use can vary significantly with the pest density volatility. Incorporating pest randomness into simple decision rules may thus help better manage the chemicals applied to soils and crops.
Efficiency and Market Power in Greek Food Industries
Authors: Oustapassidis K. , Vlachvei A. , Notta O.
Published: March 2003

This paper uses firm level data to examine the market power versus efficiency hypothesis by taking into consideration both the long‐run behavior of profitability and the possible endogeneity bias among profitability, market share, and advertising variables. In a sample of 266 Greek food manufacturing firms in the period 1987–95, two‐stage least‐squares results show both a direct effect of firm characteristics and an indirect effect of industry characteristics on profitability which do not provide support for the efficiency hypothesis alone but they do show that profitability is affected by both firm and industry variables.
Crop Insurance under Catastrophic Risk
Authors: Duncan John , Myers Robert J.
Published: March 2003

We develop a new insurance model that shows how catastrophic risk affects the nature and existence of a crop insurance market equilibrium. A reservation preference level is used to characterize long‐run equilibrium when catastrophic risk makes insurance companies risk responsive. Catastrophic risk is shown to increase premiums, reduce farmer coverage levels and, under some conditions, lead to a complete breakdown of the crop insurance market. Reinsurance can help facilitate an equilibrium and/or increase participation, particularly if the reinsurance is subsidized. The analysis has important implications for the design and management of crop insurance and reinsurance programs.
Using Consumption and Asset Return Data to Estimate Farmers' Time Preferences and Risk Attitudes
Authors: Lence Sergio H.
Published: March 2003

The generalized expected utility model is fitted to U.S. farm data to estimate farm operator's time preferences and risk attitudes. The estimated farmer's utility parameters are quite “reasonable” and exhibit high accuracy. The forward‐looking expected utility model is soundly rejected in favor of the generalized expected utility paradigm. Importantly, the generalized expected utility model is also found to fit the data better than the myopic model typically used to study agricultural production under risk. Finally, U.S. farmers' relative aversion to risk appears to have diminished significantly over time
Regional Shifts in Pork Production: Implications for Competition and Food Safety
Authors: Önal Hayri , Unnevehr Laurian , Bekric Aleksandar
Published: March 2003

U.S. pork production and processing is consolidating in larger, more economically efficient units, and shifting from the Midwest into the Southeast. A regionalmodelof farm supply and processing demand shows that smaller Midwest operations can survive only if processing capacity remains concentrated in that region. Salmonella incidence is higher in the Southeast and on larger farms. Restricting salmonella incidence in hogs delivered for processing to the minimum feasible level would increase total industry costs by 3%, due to increased production and delivery costs. It would also increase the comparative advantage of farms and processing firms in the Midwest.
Slippage Effects of the Conservation Reserve Program
Authors: Wu JunJie
Published: March 2003

Each year, billions of dollars of public funds are expended to purchase conservation easements on farmland. One unintended impact of these programs is that they may bring non‐cropland into crop production. Such a slippage effect can be caused by increased output prices and by substitution effects. This article shows that for each one hundred acres of cropland retired under the Conservation Reserve Program (CRP) in the central United States, twenty acres of non‐cropland were converted to cropland, offsetting 9% and 14% of CRP water and wind erosion reduction benefits, respectively. Implications of these results for the design of conservation programs are discussed.
Market and Cost Structure in the U.S. Beef Packing Industry: A Plant‐Level Analysis
Authors: Morrison Paul Catherine J.
Published: March 2003

A resurgence of consolidation in the U.S. meat packing industry in the past few decades has stimulated academic and policy debate. Issues raised include the role of cost economies in driving these patterns, and the effects on the agricultural sector (cattle producers) from market power. Here, plant level cost and revenue data for U.S. beef packing plants are used to estimate a cost‐based model incorporating cattle‐ and output‐market pricing behavior. The robust results indicate little market power exploitation in either the cattle input or beef output markets, and that any apparent evidence is counteracted by cost efficiencies such as utilization and scope economies.
Agricultural Export Subsidies as a Tool of Trade Strategy: Before and after the Federal Agricultural Improvement and Reform Act of 1996
Authors: Leathers Howard D.
Published: March 2003

If the main justification for agricultural export subsidies is that they reduce government costs of deficiency payments, then the 1996 farm legislation would make U.S. export subsidies largely unnecessary. An additional argument advanced in favor of export subsidies is that their aggressive use by one country will cause competing countries to reduce or discontinue their own subsidies. This argument is explored by means of a Nash equilibrium in which countries choose both a base subsidy level and a response to competitors, and by a consistent conjectures equilibrium. Little support is found for the argument.
Incorporating Quadratic Scale Curves in Inverse Demand Systems
Authors: Beach Robert H. , Holt Matthew T.
Published: March 2003

In this paper we introduce inverse demand systems that include quadratic scale terms. These systems are similar to regular quadratic demand systems introduced by Howe, Pollak, and Wales. A unique feature of these specifications is that they maintain linear scale curves as a special case. For illustrative purposes we estimate the Normalized Quadratic Inverse Demand‐Quadratic Scale System using monthly South Atlantic fish landings and valuation data, 1980‐1996. In estimation concavity is maintained locally, and the rank reduction procedures advocated by Diewert and Wales (1988a) are employed. The estimated model is then used to obtain welfare estimates associated with catch restrictions.
Spatial Market Integration in the Presence of Threshold Effects
Authors: Goodwin Barry K. , Piggott Nicholas E.
Published: March 2003

A large body of research has evaluated price linkages in spatially separate markets. Much recent research has applied models appropriate for nonstationary data. Such analyses have been criticized for their ignorance of transactions costs, which may inhibit price adjustments and thus affect tests of integration. This analysis utilizes threshold autoregression and cointegration models to account for a neutral band representing transactions costs. We evaluate daily price linkages among four corn and four soybean markets in North Carolina. Nonlinear impulse response functions are used to investigate dynamic patterns of adjustments to shocks. Our results confirm the presence of thresholds and indicate strong support for market integration, though adjustments following shocks may take many days to be complete. In every case, the threshold models suggest much faster adjustments in response to deviations from equilibrium than is the case when threshold behavior is ignored.
The Migration of Young Adults from Non‐Metropolitan Counties
Authors: Mills Bradford , Hazarika Gautam
Published: March 2003

This article examines young adult migration from non‐metropolitan counties to either different non‐metropolitan counties or to metropolitan areas. The results show that expected gains in initial earnings provide young entrants to the labor force with a marked incentive to migrate from their non‐metropolitan counties of origin. Initial earnings gains stem, in part, from higher returns to schooling in both metropolitan areas and other non‐metropolitan counties. The propensity to migrate is also sensitive to the costs of migration, which, in turn, are correlated with paternal education and the local presence of extended family.
The Role of Amenities and Quality of Life In Rural Economic Growth
Authors: Deller Steven C. , Tsai Tsung‐Hsiu (Sue) , Marcouiller David W. , English Donald B.K.
Published: March 2003

A structural model of regional economic growth is estimated using data for 2243 rural U.S. counties. Five indices designed to capture specific amenity and quality of life characteristics are constructed using fifty‐four separate indicators. Results suggest that amenity characteristics can be organized into consistent and meaningful empirical measures that move beyond ad hoc descriptions of amenities. In addition to insights into the influence of local characteristics ranging from tax burdens to income distribution on regional economic growth, results suggest that predictable relationships between amenities, quality of life, and local economic performance exist.
Market Incentives for Safe Foods: An Examination of Shareholder Losses from Meat and Poultry Recalls
Authors: Thomsen Michael R. , McKenzie Andrew M.
Published: March 2003

Meat and poultry recalls, while voluntary, are carried out under governmental oversight. If firms have financial incentives to avoid being implicated in a recall situation, governmental involvement in recalls may cause firms to internalize social costs when making investment decisions concerning food safety controls. To examine these incentives, we analyze federally supervised meat and poultry recalls from 1982 to 1998 within an event study. Results show significant shareholder losses when publicly traded food companies are implicated in a recall involving serious food safety hazards. We find no evidence that the stock market reacts negatively when recalls involve less severe hazards.
Traders' Bidding Strategies on European Grain Export Refunds: An Analysis with Affiliated Signals
Authors: Bourgeon Jean‐Marc , Roux Yves Le
Published: March 2003

Using a multivariate distribution of traders' information with correlations, we specify the traders' bidding strategies on tenders of European soft wheat intervention stocks. We show that correlations may have opposing effects on the traders' bidding strategy, depending on their valuation of the grain. This structural approach allows us to estimate the traders' strategies using generalized method of moments procedures.
Optimal Insurance Against Climatic Experience
Authors: Mahul Olivier
Published: March 2003

An optimal insurance contract against a climatic risk is derived in the presence of an uninsurable and dependent aggregate production risk. The optimaldesign depends on the stochastic dependency between both sources of uncertainty and on the producer's attitude towards risk, especially on his prudent behavior. Rationalweather insurance purchasing decisions are also derived. The prudent producer responds to actuarially fair weather insurance by increasing his exposure towards risk.
Non‐parametric Productivity Analysis with Undesirable Outputs: An Application to the Canadian Pulp and Paper Industry
Authors: Hailu Atakelty , Veeman Terrence S.
Published: March 2003

This article extends the Chavas‐Cox approach to non‐parametric analysis by incorporating undesirable outputs to provide a more complete representation of the production technology. Inner and outer non‐parametric technology bounds are constructed. The methods are illustrated with application to time series data for the Canadian pulp and paper industry. Conventional measures that ignore changes in pollutant outputs underestimate true productivity growth. Further, there is a large gap between estimates generated with reference to inner and outer bounds to the technology, suggesting that researchers need to be aware of the limitations of results derived from analyses relying only on DEA methods.
Modeling Recreation Site Choice: Do Hypothetical Choices Reflect Actual Behavior?
Authors: Haener M. K. , Boxall P. C. , Adamowicz W. L.
Published: March 2003

We examine the ability of revealed preference (RP), site‐specific stated preference (SP), transferred SP, and joint RP‐SP models to predict aggregate and individual recreation site choice in a holdout sample. For two statistical comparisons, the RP model provided the most accurate predictions of individual choices. However, the transferred SP model, applied directly or estimated jointly with the RP data, performed best in three aggregate and one individual prediction test. These findings suggest that data from well‐designed and conducted SP surveys from one site can be combined with site‐specific RP data from another site to generate improved models of recreation site choice.