bluuebunny/crossref_metadata_2025 huggingface dataset:
Managerial Inputs and the Growth of Rural Small Firms
Authors: Variyam Jayachandran N. , Kraybill David S.
Published: July 2006

Growth of rural small firms is influenced by education and work effort of owner or manager, and by degree of technology adoption and planning. Results are based on analysis of data from a small business survey in twenty‐five rural Georgia counties. Employment growth in a sample of manufacturing, sales, and service firms is examined. Independent firms, sole proprietorships, and firms owned by women are found to have significantly lower‐than‐average growth rates. The study confirms earlier findings that firm growth is negatively related to firm size and age. Implications for small business assistance programs are discussed.
A Demand Systems Analysis of Food Commodities by U.S. Households Segmented by Income
Authors: Park John L. , Holcomb Rodney B. , Raper Kellie Curry , Capps Oral
Published: July 2006

Using the 1987–88 Nationwide Food Consumption Survey, twelve food commodity groups were analyzed according to household poverty status. Parameter estimates were used to obtain subsistence expenditures, own‐price elasticities, expenditure elasticities, and income elasticities. Own‐price elasticities were similar between the income groups for most commodities. However, income elasticities were consistently higher for the lower‐income group. The use of average estimates of price and income elasticities for the population as a whole for the projection of individual commodity demands is not likely to be successful if notable changes are evident in income distribution.
Crop Insurance, Moral Hazard, and Agricultural Chemical Use
Authors: Smith Vincent H. , Goodwin Barry K.
Published: July 2006

This study examines the relationship between chemical input use and crop insurance purchase decisions for a sample of Kansas dryland wheat farmers. Recent research by Horowitz and Lichtenberg indicated that, contrary to conventional wisdom, farmers that purchased insurance tended to use relatively more chemical inputs than farmers who did not insure. In contrast, our results confirm the conventional view that moral hazard incentives lead insured farmers to use fewer chemical inputs. Implications for the joint determination of insurance and input use decisions and appropriate estimation techniques are discussed.
Intraseason Harvest Regulation for Fish and Wildlife Recreation: An Application to Fishery Policy
Authors: Swallow Stephen K.
Published: July 2006

Resource managers often ignore economic information in decisions about recreational use of fish and wildlife resources. By evaluating within‐season harvest regulations, economists can identify strategies to improve recreational benefits without compromising management objectives represented in an annual harvest quota. Theoretical analysis raises a potential for bias in applied welfare analysis if regulations inefficiently trade off fishing quality and exogenous seasonality in anglers' demand. Simulations demonstrate that efficient regulations may limit daily harvests during the best fishing season or during the peak season of demand. Inadequate knowledge of recreationists' behavioral responses to quality and regulations currently limits policy assessments.
Spatial Competition, Uniform Pricing, and Transportation Efficiency in the California Processing Tomato Industry
Authors: Durham Catherine A. , Sexton Richard J. , Song Joo Ho
Published: July 2006

This study examines the role of spatial pricing in the allocation of processing tomatoes from farms to the thirty‐two processing facilities located in northern and central California. A simple theoretical model illustrates that the industry's uniform pricing policy encourages market overlap and excessive transportation costs relative to FOB pricing. A nonlinear mathematical programming model is developed to determine the optimal allocation of processing tomatoes. This allocation is then compared to the estimated actual allocation. The analysis reveals foregone profits of only 1.9% from inefficient product allocation. Simulation results reveal significant competition among processors despite their separation in many cases by long distances.
Farmers' Investment Behavior: An Empirical Assessment of Two Specifications of Expectations
Authors: Thijssen Geert
Published: July 2006

The capital investment decision is modeled and two different assumptions about expectations are compared and tested using panel data for Dutch dairy farms. The utilization of panel data allowed to account for the possibility that the intercept in the function for capital varies over the farms. The models are estimated using the generalized method of moments (GMM) for dynamic panel data. The model based on static expectations fits the data well. The results obtained from the rational expectations model are not consistent with the theory.
An Examination of the Effects of Price Supports and Federal Crop Insurance Upon the Economic Growth, Capital Structure, and Financial Survival of Wheat Growers in the Northern High Plains
Authors: Atwood Joseph A. , Watts Myles J. , Baquet Alan E.
Published: July 2006

This study examines the effects of both farm price support programs and federally subsidized crop insurance programs upon the profitability, capital structure, and financial survival rates of High Plains wheat producers. The alternative farm programs are analyzed in an intertemporal dynamic setting. Results indicate that the producer's first response to risk is to restrict the use of debt. Price support programs and crop insurance are substitutes in reducing producer risk. The availability of crop insurance in a setting with price supports allows producers to service higher levels of debt with no increase in risk.
An Empirical Investigation of the Consistency of Nested Logit Models with Utility Maximization
Authors: Kling Catherine L. , Herriges Joseph A.
Published: July 2006

Global conditions under which nested logit models are consistent with utility maximization are provided by Daly and Zachary and by McFadden. Recently, Börsch‐Supan and Herriges and Kling have provided conditions under which a nested logit model is locally consistent. However, previous work has not discussed implementation of these conditions. Here, three alternative approaches to checking and formally testing for the consistency conditions using classical statistics are investigated. In addition, a Bayesian approach to interpreting and imposing the local consistency conditions is provided. The application is based on anglers' choices regarding sportfishing alternatives in southern California.
Farm Consumption Behavior in the Presence of Uncertainty and Restrictions on Credit
Authors: Phimister Euan
Published: July 2006

Farm consumption behavior has an important indirect role in determining the ability of farms to invest and grow. In this paper I examine the effect on farm consumption behavior of the presence of quantitative restrictions on farm borrowing. Using a form of the life cycle model which allows for both consumption and production by the household, the effect of borrowing restrictions on consumption behavior is tested econometrically for a sample of Dutch farm households. The results suggest that the life cycle model without borrowing restrictions is rejected by the data.
Hedging with Crop Yield Futures: A Mean‐Variance Analysis
Authors: Vukina Tomislav , Li Dong‐feng , Holthausen Duncan M.
Published: July 2006

This investigation into the use of new Chicago Board of Trade yield futures to manage price and yield risks shows that a risk‐minimizing firm can reduce its variance of profit by hedging in both markets compared to hedging in price futures only. The greater the variance of the contract underlying yield, the less effective the two‐instrument hedge. Hedging effectiveness of the dual strategy also depends on the price and yield bases, and the effect of a change in either basis depends on whether the established crop yield futures position is short or long.
Measuring Welfare Impacts from Equilibrium Supply and Demand Curves: An Antidumping Case Study
Authors: Canning Patrick N. , Vroomen Harry
Published: July 2006

In this paper we present an applied welfare analysis in the tradition of Harberger that confronts the notable exceptions to the appropriate use of a single market measure for general equilibrium welfare analysis. We bring together the results of several elaborative studies on Harberger's 1971 essay and present some empirical remedies that address the notable exceptions to the appropriate use of estimates made in a single market. A case study involving a U.S. antidumping suit against Canadian exports of potash is presented.
Information Asymmetry as a Reason for Food Industry Vertical Integration
Authors: Hennessy David A.
Published: July 2006

Three trends that have been subject to recent discussion are a movement away from undifferentiated agricultural commodities toward more specialized products, reduced reliance on open markets for raw agricultural products, and a movement toward agricultural industrialization. Recent research suggests that demographic trends may be causing the first trend, while the other two are closely related phenomena. This research suggests that information externalities, arising from uncertainty concerning the nature of food quality and problems in detecting quality, may be reasons why vertical coordination is being used to circumvent the marketplace.
The Timing of Land Development: An Invariance Result
Authors: Batabyal Amitrajeet A.
Published: July 2006

The Arrow‐Fisher‐Henry (AFH) analysis of land development under uncertainty has been conducted in a two‐period model. Recently, Capozza and Helsley (1990) and Batabyal (1995) have addressed the question of land development under uncertainty in a many‐period setting. In this paper, aspects of this literature are extended by analyzing the land development question in a Markov decision theoretic framework. Inter alia, it is shown that the timing of land development is invariant to the manner in which a landowner uses information about the consequences of development.
Technology as an Agricultural Pollution Control Policy
Authors: Abler David G. , Shortle James S.
Published: July 2006

In this paper we consider the market‐level impacts of factor‐augmenting innovations designed to reduce the use of fertilizers and pesticides, first within the context of a simple two‐factor model, and then through a simulation model of the U.S. corn market. In both models, the impacts depend on the output demand elasticity and input substitution elasticities. The principal conclusion of the simulation analysis is that the potential for new techniques to reduce the use of agricultural chemicals is limited. Capital‐augmenting innovations would actually raise fertilizer and pesticide usage. Land‐augmenting innovations would also tend to increase pesticide usage.
Damage Control and Increasing Returns
Authors: Fox Glenn , Weersink Alfons
Published: July 2006

The indirect action of damage control inputs means the marginal productivity of these inputs depends on their effectiveness in controlling the level and size of production loss caused by the damage agent. Increasing returns to damage control inputs can occur even when control and damage functions are concave. The result implies more attention needs to be paid to the functional form selection for damage and control functions in empirical work on pest control and other types of damage control inputs. In addition, the possibility of increasing returns may undermine the general use of taxes to reduce pesticide use.
The Conservation Reserve Program as a Least‐Cost Land Retirement Mechanism
Authors: Smith Rodney B.W.
Published: July 2006

Mechanism design theory is used to characterize the properties of a least‐cost CRP. If marginal land rents decrease with acres farmed then a least‐cost CRP is a set of nonlinear price schedules. If marginal land rents are independent of acres farmed then an offer system constitutes a least‐cost CRP. The least‐cost offer system gives a useful estimate of the upper bound of a least‐cost CRP. Empirical results suggest that a 34‐million‐acre CRP should have cost no more than $@@‐@@1 billion per year.
Using Random Utility Models to Estimate the Recreational Value of Estuarine Resources
Authors: Kaoru Yoshiaki , Smith V. Kerry , Liu Jin Long
Published: July 2006

In this paper we describe a model using a household production framework to link measures of nonpoint source pollution to fishing quality and a random utility model to describe how that quality influences sport fishing parties' decisions in North Carolina. The results provide clear support for using a model that evaluates the effects of pollution on the activities and decisions associated with the fishing activity once a trip is taken. Site selection decisions are then conditioned on the anticipated quality of fishing sites. The framework also has the advantage of linking the spatial, technical, and economic information required to evaluate the management plans required for estuaries under the National Estuarine Program.
Depreciation Patterns for Agricultural Machinery
Authors: Cross Timothy L. , Perry Gregory M.
Published: July 2006

A flexible functional form model is used to estimate remaining‐value equations for eleven major types of farm machinery. Data used in estimation were obtained from ten years of machinery auctions. Remaining values were found to be influenced by machinery condition, use, manufacturer, and age. Macroeconomic variables were significant explanatory variables for most types of machinery. Estimated depreciation patterns varied by machinery type, demonstrating the need for updated machinery‐specific remaining‐value equations. Reduced‐form equations are presented for use in applied economic analysis.
A Dual Approach to Evaluating Research Benefits in the Presence of Trade Distortions
Authors: Martin Will J. , Alston Julian M.
Published: July 2006

We present a new approach for evaluating the welfare consequences of technical change. A major feature is its ability to incorporate multiple distortions and multiple sources of technical change in interrelated markets. A modified balance‐of‐trade function provides money measures of welfare change in terms of producer profits, consumer expenditures, and tax revenues. Alternative specifications of technical change are presented to capture the effects of differences in the form of technical change. In an illustrative numerical example, the approach is applied to a case involving two distortions and technical changes in two related markets. The example shows that the approach is reasonably easy to use and that accounting correctly for price distortions can have important implications for research benefit measures.
Predicting the Effects of Market Reform in Zimbabwe: A Stated Preference Approach
Authors: Rubey Lawrence , Lupi Frank
Published: July 2006

A stated preference approach is used to predict likely responses to market reform in Zimbabwe. A random utility model is estimated using data on consumers' stated preferences for alternative types of maize meal. The model is used to predict demand patterns resulting from market reforms. Predicted demand is then compared with actual demand following market reforms. An analysis of the welfare effects of alternative policy scenarios shows that coupling the removal of consumer maize subsidies with improved access to a broader range of maize meal products ameliorated many of the adverse effects of subsidy removal, especially for lower‐income groups.
Product Aggregation Bias as a Specification Error in Demand Systems
Authors: Davis George C.
Published: July 2006

Inherent in all demand studies is some form of product aggregation which can lead to product aggregation bias. This article develops a simple procedure for incorporating product aggregation bias in demand systems that permits testing of product aggregation bias with a standard likelihood ratio test. An empirical illustration of the procedure demonstrates the importance of proper product aggregation.
Dynamic Adjustment in Vertically Linked Markets: The Case of the U.S. Beef Industry
Authors: Buhr Brian L. , Kim Hanho
Published: July 2006

This duality model is used to investigate the dynamic structure of vertically linked sectors of the U.S. beef industry. The model employed allows for explicit hypothesis tests of the adjustment process and technology change. Vertically related sectors of the beef industry are included to emulate the organizational structure of the industry. Results suggest that the cow‐calf, feedlot, and beef processing sectors of the U.S. industry face significant adjustment costs. Another important finding is that imports may provide a way for the U.S. beef industry to adjust to short‐run market changes.
Calibrating Benefit Function Transfer to Assess the Conservation Reserve Program
Authors: Feather Peter , Hellerstein Daniel
Published: July 2006

Benefit transfer offers an inexpensive alternative to conducting an original study to determine economic value. Unfortunately, benefit transfers can also result in biased welfare estimates. In this paper, we suggest a method of calibrating the benefit transfer to reduce this bias. An empirical example to determine the benefits of the Conservation Reserve Program on water‐based recreation illustrates the potentially large biases that can result if the transfer is not calibrated.
Expo‐Power Utility: A ‘Flexible’ Form for Absolute and Relative Risk Aversion
Authors: Saha Atanu
Published: July 2006

A new utility function, which I call expo‐power, is proposed that exhibits decreasing, constant, or increasing absolute risk aversion and decreasing or increasing relative risk aversion, depending on parameter values. Numerical analysis suggests that the expo‐power function performs well in incorporating these risk preference structures, and that arbitrary risk preference specifications may lead to biased risk response estimates.
The Economics of Reentry Regulation of Pesticides
Authors: Lichtenberg Erik , Spear Robert C. , Zilberman David
Published: July 2006

Government agencies frequently try to protect the public from industrial hazards by separating the two in time and/or space. This paper develops a methodology for one such policy, reentry regulation of pesticides. Re‐entry regulation is shown to provide a rational incentive for preventive applications of pesticides, a practice usually attributed to risk aversion or inadequate information. The tradeoffs between farm worker poisonings and lost grower revenue are shown to be substantial. Weather‐dependent, location‐specific reentry regulation appears superior to the uniform regulation now in effect.
Rationalizing Agricultural Export Subsidies
Authors: Alston Julian M. , Carter Colin A. , Smith Vincent H.
Published: July 2006

A conventional view is that export subsidies are inferior to output subsidies as a means of supporting farm prices. However, when there is an excess burden associated with general taxation measures, due to the distortions in markets arising from collection of taxes and any other costs associated with tax collections, export subsidies may be a component of the most efficient producer price support policy. The arguments in this paper provide a more persuasive rationale for pervasive agricultural export subsidies than does much of the recent literature.
Income Taxes and Price Variability in Storable Commodity Markets
Authors: McNew Kevin , Gardner Bruce
Published: July 2006

Progressive income taxes lead to distortions in economic decisions made across tax years. This is particularly important when income is volatile, as in the case of agriculture. Progressive taxes, therefore, can fundamentally change economic behavior over time. This study explores how progressive income taxes influence storage decisions and the markets for storable commodities. Under a progressive tax system, commodity storage tends to be lower in the aggregate and, as a consequence, price volatility increases. These distortions could be eliminated by introducing a flat‐rate tax or by changing the tax reporting system for farmers.
Hysteresis and the Shortage of Agricultural Labor
Authors: Richards Timothy J. , Patterson Paul M.
Published: July 2006

Fruit and vegetable growers often allege a shortage of agricultural workers, but in a review of the H2A nonimmigrant guestworker program the General Accounting Office claims that no such shortage exists. The apparent shortage may be due to workers that are in the labor force but do not choose to take agricultural jobs. According to real options theory, when nonagricultural jobs are uncertain, workers require added incentive to invest in sectoral migration. Estimates of an arbitrage model in monthly Washington state wage data show the labor‐shortage probability to be far greater than the probability of a surplus.
Returns to Public Investments in Agriculture with Imperfect Downstream Competition
Authors: Hamilton Stephen F. , Sunding David
Published: July 2006

A multiple‐market framework is developed to measure the size and distribution of research benefits. The model considers an upstream raw product market and a downstream finished productmarket and allows for imperfect competition in the intermediary food‐processing sector. A central conceptual result is derived: an increase in raw product output is a sufficient condition for cost‐reducing innovations in the farm sector to increase social welfare. A special case of linear farm supply and isoelastic processing production functions reveals that necessary conditions for welfare to decrease are a convergent farm supply shift, an oligopsonistic upstream market configuration, and increasing returns‐to‐scale processing technology.
Tenure Security, Investment and Productivity in Gambian Agriculture: A Generalized Probit Analysis
Authors: Hayes Joseph , Roth Michael , Zepeda Lydia
Published: July 2006

The determinants of investment, input use, and productivity are investigated under customary tenure in peri‐urban areas of the Gambia. A structural model is specified to investigate the role of tenure security on farm investments and input use and thereby on yield. Testing of the structural form hypotheses requires simultaneous equation estimation. Containing both continuous and discrete endogenous variables, the model is estimated as a feasible generalized least squares Amemiya's generalized probit. Some of the positive relationships hypothesized between tenure security, investment, and yields are corroborated. In particular, tenure security is found to enhance long‐term investments, which in turn enhance yields.
Hedonic Cost Models and the Pricing of Milk Components
Authors: Buccola Steven , Iizuka Yoko
Published: July 2006

To assess likely producer response to milk price reform, we examine the technology of protein, butterfat, and fluid carrier production on 1,924 U.S. dairy farms. A variant of a hedonic cost model is proposed in which the output aggregator is expressed as a function of total output and of the percentage concentrations of its components. Dairy farmers have responded rationally to artificially low protein prices. Due to the cow's appetite limit, farmers operate in stage I of feed‐to‐milk production functions; yet protein's marginal cost rises sharply with protein output. Only modest substitutability is evident among feed inputs or milk component outputs.
Reducing Yield Variation in Peach Orchards by Geographic Scattering
Authors: Davis Stephen B. , Price T. Jeffrey , Wetzstein Michael E. , Rieger Mark W.
Published: July 2006

Assuming a declining correlation in yields as distance between pairs of orchards increases, yield variability in peach production may be reduced by increasing distances among orchards. As a measure of yield variability that avoids possible bias resulting from orchard‐specific effects, a stochastic production function is estimated. Results support the assumption that a declining correlation between yields exists as distance increases. For every mile further apart, the correlation in yield declines 2.28%.
Potential Demand for Drought Insurance in Burkina Faso and Its Determinants
Authors: Sakurai Takeshi , Reardon Thomas
Published: July 2006

The objectives of this paper are twofold: (a) to estimate demand for formal drought insurance using farm household data in Burkina Faso and (b) to find what determines insurance demand. The following findings are salient. First, effective demand is found in all zones, which implies inadequacies in households' current self‐insurance strategies. Second, there is much heterogeneity in the strategies to self‐insure even within zones. Third, the expectation of public food aid decreases demand for drought insurance, which suggests that food aid is causing moral hazard. Fourth, households with large livestock holdings can reduce the size of herd by substituting drought insurance for livestock holdings.
Priorities and Preferences in the Allocation of MPP Branded Funds to Agribusiness Firms
Authors: Adams Barry H. , Davis George C. , Jensen Kim L. , Jakus Paul M.
Published: July 2006

In 1993, legislation was passed that required the USDA to give priority in the allocation of its Market Promotion Program (MPP) branded funds to small firms, new‐to‐export firms, and firms facing exporting problems in foreign markets. However, the MPP is still criticized in the popular press and by the General Accounting Office as favoring large and existing exporting firms that do not face exporting problems. Using a unique firm‐level data set, the effectiveness of the 1993 legislation is evaluated by analyzing the allocation of MPP funds according to firm characteristics and the priorities set in the 1993 legislation.
Asymmetric Adjustment of Dynamic Factors at the Firm Level
Authors: Lansink Alfons Oude , Stefanou Spiro E.
Published: July 2006

This study provides a framework for consistent estimation of a dynamic dual model of investment for the case where data reveal zero and nonzero investments. The threshold model that is developed maintains that investments are zero if the shadow value of machinery is between a lower and an upper threshold. Separate equations are estimated for the investment and the disinvestment regime. A significant difference between the parameters of the investment and disinvestment equations is found. The stock of machinery adjusts slower toward the long‐run equilibrium target during an investment regime than during a contracting regime.
A Soil‐Quality Index and Its Relationship to Efficiency and Productivity Growth Measures: Two Decompositions
Authors: Jaenicke Edward C. , Lengnick Laura L.
Published: July 2006

This article reconciles two notions of soil‐quality indexes with the economic concepts of technical efficiency and productivity growth. An example uses data from the U.S. Department of Agriculture's experimental fields in Maryland and data envelopment analysis techniques to estimate a soil‐quality index consistent with the notion of technical efficiency. Common regression techniques shed additional light on the role of individual soil‐quality properties in a very restricted linear approximation of the estimated soil‐quality index.
Using Cross‐Section Data to Adjust Technical Efficiency Indexes Estimated With Panel Data
Authors: Álvarez Antonio M. , González Eduardo
Published: July 2006

This article proposes a procedure to incorporate cross‐sectional information in the estimation of technical efficiency indexes obtained from panel data. A conventional index of technical efficiency is estimated in a first stage using panel data on inputs and outputs. The individual effects from the first stage are then adjusted using cross‐sectional information, obtaining a corrected technical efficiency index. The model is applied to a panel of eighty‐two Spanish dairy farms, where only cross‐sectional information about input quality is available. An analysis of variance is performed between some variables and both the corrected and the uncorrected indexes, finding that the conclusions derived from the two analyses are different.
Price Information and Bidding Behavior in Repeated Second‐Price Auctions
Authors: List John A. , Shogren Jason F.
Published: July 2006

Examining panel data on bidding behavior in over forty second‐price auction markets with repeated trials, we observe that (i) posted prices influence the behavior of the median naive bidder; (ii) posted prices do not affect the behavior of the median experienced bidder or the bidder for familiar goods; and (iii) anticipated strategic behavior wanes after two trials. The results suggest that while affiliation might exist in auctions for new goods, the repeated trial design with nonprice information removes the correlation of values and provides the experience that bidders need to understand the market mechanism.
Education in Production: Measuring Labor Quality and Management
Authors: Yang Dennis Tao
Published: July 2006

Production function studies have used the education of the head of the household or the average education of farm workers to assess the contribution of schooling to farm efficiency. In this paper I critically examine the information content of these measures by developing a team production model which suggests separate education measures to approximate labor quality and managerial skills. Empirical analyses based on Chinese farm household data show that the new measures are statistically superior to the existing alternatives. There is evidence of centralized decision making on the farms where the highest schooling contributes the most to production efficiency.
New Evidence on Agricultural Commodity Return Performance under Time‐Varying Risk
Authors: Bjornson Bruce , Carter Colin A.
Published: July 2006

Holding commodity stocks is a major investment that commodity producers, merchants, and processors must continually manage. In this paper we study the conditional risk and return characteristics of commodities. We use a generalized method of moments estimator in a model of conditional expected returns under a single‐beta asset pricing theory framework, allowing both the risk premium and the beta to vary with time. We find that expected returns to commodities are lower during times of high interest rates, expected inflation, and economic growth. This suggests that commodities provide a natural hedge against business cycles.
Agricultural Policies in the Presence of Distorting Taxes
Authors: Parry Ian W.H.
Published: July 2006

This article analyzes how distortionary factor taxes affect the welfare impacts of production subsidies, production quotas, acreage controls, subsidies for acreage reductions, and cash transfers to farmers. Pre‐existing taxes substantially raise the costs of all these policies. These additional costs reflect the welfare losses from financing certain policies by distortionary taxes. They also reflect interactions with factor markets caused by changes in the costs of producing agricultural output. Previous studies ignore the latter types of effect. Consequently they significantly overstate the costs of production subsidies and understate the costs of production quotas, acreage controls, and subsidies for acreage reductions.
Modeling Recreation Demand in a Poisson System of Equations: An Analysis of the Impact of International Exchange Rates
Authors: Englin Jeffrey , Boxall Peter , Watson David
Published: July 2006

We extend count data travel cost modeling by developing a utility theoretic system of semilogarithmic recreation demand equations. The restrictions required to make the system utility theoretic are applied during estimation. The model is applied to individual wilderness recreation trips in a system of four Canadian wilderness parks. The resulting demand system is used to examine the impacts of changing U.S.‐Canadian currency exchange rates on participation and welfare of U.S. recreationists.
Option Values to Conservation and Agricultural Price Policy: Application to Terrace Construction in Kenya
Authors: Winter‐Nelson Alex , Amegbeto Koffi
Published: July 2006

Policy reforms to liberalize agricultural markets in developing countries are likely to influence both the level and the variability of prices. While considerable attention has been given to the impact of changes in price level on soil and water conservation, there has been relatively little analysis of the role of price variability in conservation decisions. We present a model of investment under uncertainty to analyze the effect of both level and variability of prices on the decision to invest in conservation. The model is applied to adoption of fanya juu terraces in eastern Kenya.
Are Crop Yields Normally Distributed?
Authors: Just Richard E. , Weninger Quinn
Published: July 2006

The evidence for nonnormality of crop yields is reassessed. Three methodological problems are identified in typical yield distribution analyses: (i) misspecification of the nonrandom components of yield distributions, (ii) missreporting of statistical significance, and (iii) use of aggregate timeseries (ATS) data to represent farm‐level yield distributions. One or more of these problems infect virtually all evidence against normality to date. The positive contribution of the article is a set of principles that must be followed in any valid investigation of yield normality.
Captive Supplies, Market Conduct, and the Open‐Market Price
Authors: Azzam Azzeddine
Published: July 2006

In this paper I examine the anatomy of the price captive‐supplies relationship to ascertain if some of the interpretations offered in the empirical literature are defensible. Gardner's one‐product, two‐input model is extended to consider a partially integrated oligopsonistic industry. The main result is that, although the empirical relationship between captive supplies and the price received by independent producers is negative, it may or may not be attributed to noncompetitive conduct. Hence, for an econometric model to detect what type of conduct the relationship reflects, more structural detail is needed than what so far has been provided in the literature.
Coronary artery rupture during balloon angioplasty, rescued with localized thrombin injection and coil embolization
Authors: Fischell Tim A. , Carter Andrew J. , Ashraf Kamal , Birdsall Joseph , Smoker Sandy
Published: July 2006

Distal intracoronary thrombin injection has been used successfully to seal very small, guidewire related, coronary artery perforations during percutaneous coronary intervention. This case report expands upon this therapeutic approach, by describing the use of high dose distal thrombin injection for the successful (non‐surgical) management of balloon‐induced coronary artery rupture, with an intrapericardial leak. © 2006 Wiley‐Liss, Inc.
The Design and Synthesis of Human Branched‐Chain Amino Acid Aminotransferase Inhibitors for Treatment of Neurodegenerative Diseases.
Authors: Hu Lain‐Yen , et al. et al.
Published: July 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Microscopic theory of quantum dot luminescence spectra
Authors: Gies Christopher , Baer Norman , Wiersig Jan , Jahnke Frank
Published: July 2006

We employ a microscopic semiconductor theory to study the frequency‐resolved stationary photoluminescence spectrum of an initially excited quantum dot system. Carrier‐carrier correlations are included beyond the Hartree‐Fock level, and the influence of these correlations on the spectrum is investigated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Equilibration of two‐dimensional excitons in an in‐plane harmonic potential
Authors: Vörös Z. , Snoke D. W. , Pfeiffer L. , West K.
Published: July 2006

In this paper we report on the equilibration dynamics of spatially indirect 2D excitons in a coupled quantum well structure, trapped by an in‐plane harmonic potential. We use the size of the exciton cloud as a measure of the temperature of particles. We show that the repulsive exciton‐exciton interaction plays a major role in the time‐evolution of the cloud size, and that at low lattice temperatures the exciton temperature is higher than that of the lattice, even long after equilibrium has obviously been reached. In the final part of the paper we demonstrate how our results can also be used for determining the absolute exciton density. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Terahertz photoconductivity in GaAs/AlGaAs and HgTe/HgCdTe quantum Hall devices
Authors: Stellmach C. , Bonk R. , Vasilyev Y.B. , Hirsch A. , Hein G. , Becker C.R. , Nachtwei G.
Published: July 2006

We present measurements of the THz photoconductivity on different quantum Hall systems. GaAs/AlGaAs and HgTe/HgCdTe (MCT) heterostructures with Hall‐bar and Corbino geometry are investigated. A recipe for the preparation of metallic Corbino contacts on MCT is shown. The system is excited by the radiation of a p ‐Ge laser (tunable from 1.7 to 2.5 THz) and the photoresponse (PR) is measured versus the magnetic field B . We observe enhanced PR around integer filling factors (bolometric PR) and cyclotron resonance (CR) effects. Because of the lower effective mass in MCT, the CR in this system appears at a relatively low magnetic field (≈2 T). This is appropriate for possible applications. Finally we present time resolved measurements of the PR on the GaAs system. We find relaxation times from about 10 to over 200 ns, which depend on the geometry, the applied source‐drain voltage and the on mobility of the sample. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unfolding single RNA molecules: bridging the gap between equilibrium and non-equilibrium statistical thermodynamics
Authors: Bustamante Carlos
Published: July 2006

During the last 15 years, scientists have developed methods that permit the direct mechanical manipulation of individual molecules. Using this approach, they have begun to investigate the effect of force and torque in chemical and biochemical reactions. These studies span from the study of the mechanical properties of macromolecules, to the characterization of molecular motors, to the mechanical unfolding of individual proteins and RNA. Here I present a review of some of our most recent results using mechanical force to unfold individual molecules of RNA. These studies make it possible to follow in real time the trajectory of each molecule as it unfolds and characterize the various intermediates of the reaction. Moreover, if the process takes place reversibly it is possible to extract both kinetic and thermodynamic information from these experiments at the same time that we characterize the forces that maintain the three-dimensional structure of the molecule in solution. These studies bring us closer to the biological unfolding processes in the cell as they simulate in vitro, the mechanical unfolding of RNAs carried out in the cell by helicases. If the unfolding process occurs irreversibly, I show here that single-molecule experiments can still provide equilibrium, thermodynamic information from non-equilibrium data by using recently discovered fluctuation theorems. Such theorems represent a bridge between equilibrium and non-equilibrium statistical mechanics. In fact, first derived in 1997, the first experimental demonstration of the validity of fluctuation theorems was obtained by unfolding mechanically a single molecule of RNA. It is perhaps a sign of the times that important physical results are these days used to extract information about biological systems and that biological systems are being used to test and confirm fundamental new laws in physics.
Word-initial clusters and minimality in Yakima Sahaptin
Authors: Hargus Sharon , Beavert Virginia
Published: July 2006

In the Yakima dialect of Sahaptin, the smallest forms of words are CCV and CVC, as established by a study of lexical patterns and the obligatory augmentation of subminimal roots. We argue that CCV words cannot be considered a type of disyllable, nor do the initial consonants in CCV words exhibit properties (apart from minimality) that would allow them to be classified as moraic. We therefore propose that Yakima Sahaptin represents a previously unrecognised type of minimality, biconsonantal minimality. This kind of minimality requires a theoretical framework in which consonants can be distinguished from vowels, as do other phonological phenomena.
Treatment of osteoporosis in old age
Authors: Jay Roger H
Published: July 2006

Osteoporosis is defined in adults as having a bone mineral content at the lumbar spine or hip of more than 2.5 standard deviations below the expected mean for the healthy young sex-matched population (WHO criteria). Osteoporosis and consequent fragility fractures are common problems, increasing in frequency with age. Several classes of drug of proven value in reducing the risk of osteoporotic fractures are now available. This review will examine how the evidence that treatment of osteoporosis reduces fracture risk applies specifically to older people, particularly those over 70 years of age.
Seasonal Profiles of Sulphur, Phosphorus, and Potassium in Norway Spruce Wood
Authors: Barrelet T. , Ulrich A. , Rennenberg H. , Krähenbühl U.
Published: July 2006

Abstract: Seasonal profiles of sulphur, phosphorus, and potassium content in the wood of trees have been established for the first time. This became possible by using a novel laser ablation system coupled to HR‐ICP‐MS for measuring these elements in Norway spruce drill cores. This technique combines excellent spatial resolution with superior detection power, and makes it possible to measure low element concentrations even in relatively narrow annual rings. Despite its low quantity in wood, sulphur is an important macronutrient for plants and seems to display seasonal variations of its concentration, which correspond to actual theories of sulphur metabolism in plants. A similar seasonal pattern was also found for phosphorus, another crucial element in tree nutrition. This was unexpected, because it was previously assumed that the distribution of phosphorus remains constant throughout the year. Potassium, the third element measured, seems to be especially accumulated in the latewood. The profiles presented in this article suggest a seasonal variation, revealing some new aspects of Norway spruce (Picea abies) metabolism.
Potential organic and inorganic N uptake by six Eucalyptus species
Authors: Warren C. R.
Published: July 2006

There are no published studies of organic N uptake by species of south-eastern Australia (e.g. Eucalyptus) despite several studies of ecosystem N cycling. This study examines uptake of nitrate, ammonium and glycine (an amino acid) by six species of 16-year-old Eucalyptus growing at two plantations (‘common gardens’). By using two plantations, one xeric / oligotrophic and one mesic / eutrophic, I was able to disentangle genotypic from phenotypic differences in preference for N forms. Measurements were made on three separate occasions during spring. N uptake was examined in situ with attached roots placed in uptake solutions containing equimolar 100 μmol L–1 concentrations of 15N-nitrate, 15N-ammonium and 2-13C215N-glycine. Water and KCl extracts were used to determine the relative abundances of nitrate, ammonium and amino acids at the two plantations. Nitrate dominated at the eutrophic site, but was nearly absent at the oligotrophic site. N at the oligotrophic site was dominated by ammonium and amino acids which were present in similar concentrations. The rate of uptake of ammonium (6.3 ± 0.4 μmol g h–1; mean ± s.e., n = 108), was faster than glycine (3.4 ± 0.2), which was faster than nitrate (0.62 ± 0.07). Plant ‘preference’ for N forms did not vary between sites despite large differences in the relative abundances of N forms (nitrate v. ammonium v. amino acids). Hence, there was little evidence for acclimation of Eucalyptus species to differences in the relative availability of N forms. This study suggests the possibility for considerable organic N uptake in the field. Previous studies of ecosystem N cycling in south-eastern Australia have only examined inorganic N. The N cycle in south-eastern Australia needs to be revisited with a new perspective, one that considers inorganic N and organic N.
Casein kinase 2-dependent serine phosphorylation of MuSK regulates acetylcholine receptor aggregation at the neuromuscular junction
Authors: Cheusova Tatiana , Khan Muhammad Amir , Schubert Steffen Wolfgang , Gavin Anne-Claude , Buchou Thierry , Jacob Germaine , Sticht Heinrich , Allende Jorge , Boldyreff Brigitte , Brenner Hans Rudolf , Hashemolhosseini Said
Published: July 2006

The release of Agrin by motoneurons activates the muscle-specific receptor tyrosine kinase (MuSK) as the main organizer of subsynaptic specializations at the neuromuscular junction. MuSK downstream signaling is largely undefined. Here we show that protein kinase CK2 interacts and colocalizes with MuSK at post-synaptic specializations. We observed CK2-mediated phosphorylation of serine residues within the kinase insert (KI) of MuSK. Inhibition or knockdown of CK2, or exchange of phosphorylatable serines by alanines within the KI of MuSK, impaired acetylcholine receptor (AChR) clustering, whereas their substitution by residues that imitate constitutive phosphorylation led to aggregation of AChRs even in the presence of CK2 inhibitors. Impairment of AChR cluster formation after replacement of MuSK KI with KIs of other receptor tyrosine kinases correlates with potential CK2-dependent serine phosphorylation within KIs. MuSK activity was unchanged but AChR stability decreased in the presence of CK2 inhibitors. Muscle-specific CK2β knockout mice develop a myasthenic phenotype due to impaired muscle endplate structure and function. This is the first description of a regulatory cross-talk between MuSK and CK2 and of a role for the KI of the receptor tyrosine kinase MuSK for the development of subsynaptic specializations.
The post‐thrombotic syndrome: progress and pitfalls
Authors: Kahn Susan R.
Published: July 2006

The post‐thrombotic syndrome (PTS) develops in up to one half of patients after symptomatic deep venous thrombosis (DVT) and is the most common complication of DVT. Typical features of PTS include chronic pain, swelling, heaviness, oedema and skin changes in the affected limb. In severe cases, venous ulcers may develop. The frequency of PTS is likely to be reduced by preventing DVT with the use of effective thromboprophylaxis in high‐risk patients and settings and by minimising the risk of ipsilateral DVT recurrence. Use of compression stockings for 2 years after DVT appears to reduce the incidence and severity of PTS but issues remain regarding their use and effectiveness. Future research should focus on elucidating the pathophysiology and risk factors for PTS, assessing the safety and effectiveness of catheter‐directed thrombolysis to prevent PTS and evaluating the optimal use of compression stockings to prevent and treat PTS. In addition, new therapies to treat PTS should be sought and evaluated.
An overview of factors affecting the disposition of intramammary preparations used to treat bovine mastitis
Authors: GEHRING R. , SMITH G. W.
Published: July 2006

The administration of antimicrobial drugs by the intramammary route offers a convenient option for the treatment of bovine mastitis. The goal of antimicrobial treatment is to achieve effective drug concentrations at the site of infection. Drug concentrations must also decrease to safe levels before the milk is harvested for human consumption. The rate of change of drug concentrations in the milk and udder tissues over time is dependent on the physicochemical characteristics of the drug and how these interact with the biological environment, affecting the rate and extent of absorption, distribution and elimination. Studies reported in the literature have identified various pathophysiological and pharmaceutical factors that may influence these processes. This review summarizes current understanding of factors affecting the disposition of drugs following intramammary administration. Areas of incomplete knowledge requiring further research have been identified.