MICRO VERSUS MACRO ACREAGE RESPONSE MODELS: DOES SITE-SPECIFIC INFORMATION MATTER?

Because requisite micro data frequently are unavailable, it is common practice to use aggregate data to estimate economic relationships representing the behavior of individual agents. A substantial body of literature has examined conditions under which inferences between micro and aggregate specifications can be made. Less attention has been focused on the relative accuracy of predictions for each scale of model. In an empirical application, we compare the goodness-of-fit measures of eight sets of acreage response models, varying in aggregation from field- (micro-) level to regional- (macro-) level models. Results suggest aggregate models are superior to the micro model in predicting acreage response, even thought the micro models contain substantially more data on site-specific characteristics.Agribusiness,

EFFICIENT PATTERNS OF CONSERVATION ACTIVITIES IN A WATERSHED: THE CASE OF THE GRANDE RONDE RIVER, OREGON

This research examines a spatially explicit allocation of habitat restoration activities in an Oregon watershed to meet water temperature targets for the benefit of endangered salmonid fish species. Integrating hydrological, biological and economic models, a series of optimization problems are investigated for different policy targets including temperature reductions and enhanced fish populations. Results indicated that the heterogeneous nature of riparian conditions and stream morphology needs to be considered if restoration activities are to be allocated efficiently in a watershed. We also found that it is less costly to implement restoration activities in tributaries if the objective is to maximize stream length where water temperatures decrease by a certain degree. Although temperature reductions are primarily achieved by shading in nearby reaches, if a desired level of temperature reductions increases, then it is necessary to apply restoration efforts in remote reaches.Resource /Energy Economics and Policy,

AMENITIES IN AN URBAN EQUILIBRIUM MODEL: RESIDENTIAL DEVELOPMENT IN PORTLAND, OREGON

This paper analyzes the effect of open space and other amenities on housing prices and development density within the framework of an urban equilibrium model. The model is estimated as a system of equations that includes households' residential choice decisions and developers' development decisions and emphasizes the importance of amenities in the formation of development patterns and property values. The model is applied to Portland, Oregon, where ambitious open space programs have been implemented. The results suggest that amenities are important: households are willing to pay more for newer houses located in areas of less dense development, with more open space, better views, less traffic congestion, and near amenity locations. For the developer, increases in housing prices result in an attempt to provide more and larger houses. The attempt to provide more houses, however, results in higher density, which will ultimately reduce prices. A simulation analysis evaluates the policy implications of the model results and indicates substantial benefits from alterations in housing patternsCommunity/Rural/Urban Development, R11, R21, R31,

Experimental Constraints on Scharm-Stop Flavor Mixing and Implications in Top-quark FCNC Processes

We examine experimental constraints on scharm-stop flavor mixing in the minimal supersymmetric standard model, which arise from the experimental bounds on squark and Higgs boson masses, the precision measurements of W-boson mass and the effective weak mixing angle, as well as the experimental data on B_s-\bar B_s mixing and b -> s gamma. We find that the combined analysis can put rather stringent constraints on \tilde{c}_L-\tilde{t}_L and \tilde{c}_L-\tilde{t}_R mixings. As an illustration for the effects of such constraints, we examine various top-quark flavor-changing neutral-current processes induced by scharm-stop mixings at the LHC and find that their maximal rates are significantly lowered.Comment: B_s mass difference constraint added (version in PRD, rapid communication

Assessing the Costs and Environmental Consequences of Agricultural Land Use Changes: A Site-Specific, Policy-Scale Modeling Approach

The growth in federal conservation programs has created a need for policy modeling frameworks capable of measuring micro-level behavioral responses and macro-level landscape changes. This paper presents an empirical model that predicts crop choices, crop rotations, and conservation tillage adoption as a function of conservation payment levels, profits, and other variables at more than 42,000 agricultural sites of the National Resource Inventory (NRI) in the Upper Mississippi River Basin. Predicted changes in crop choices and tillage practices are then fed into site-specific environmental production functions to determine changes in nitrate runoff and leaching and in water and wind erosion at each NRI site. This policy-scale model is applied to the case of green payments for the adoption of conservation practices (conservation tillage and crop rotations) in the Upper Mississippi River Basin, a region under scrutiny as a significant source of nutrient loadings to the Mississippi River, causing hypoxia in the Gulf of Mexico. Results from this application suggest that payments for conservation tillage and crop rotations increase the use of these conservation practices. However, the acreage response is inelastic and the programs are not likely to be cost effective on their own for addressing the hypoxia problem in the Gulf of Mexico.agricultural policy, conservation practices, green payments, land use changes, nitrate runoff and leaching, non-point pollution, soil erosion.

Weak ties: Subtle role of information diffusion in online social networks

As a social media, online social networks play a vital role in the social information diffusion. However, due to its unique complexity, the mechanism of the diffusion in online social networks is different from the ones in other types of networks and remains unclear to us. Meanwhile, few works have been done to reveal the coupled dynamics of both the structure and the diffusion of online social networks. To this end, in this paper, we propose a model to investigate how the structure is coupled with the diffusion in online social networks from the view of weak ties. Through numerical experiments on large-scale online social networks, we find that in contrast to some previous research results, selecting weak ties preferentially to republish cannot make the information diffuse quickly, while random selection can achieve this goal. However, when we remove the weak ties gradually, the coverage of the information will drop sharply even in the case of random selection. We also give a reasonable explanation for this by extra analysis and experiments. Finally, we conclude that weak ties play a subtle role in the information diffusion in online social networks. On one hand, they act as bridges to connect isolated local communities together and break through the local trapping of the information. On the other hand, selecting them as preferential paths to republish cannot help the information spread further in the network. As a result, weak ties might be of use in the control of the virus spread and the private information diffusion in real-world applications.Comment: Final version published in PR

New physics effects on top quark spin correlation and polarization at the LHC: a comparative study in different models

Extensions of the Standard Model often predict new chiral interactions for top quark, which will contribute to top quark spin correlation and polarization in $t\bar{t}$ production at the LHC. In this work, under the constraints from the current Tevatron measurements, a comparative study of the spin correlation and polarization is performed in three new physics models: the minimal supersymmetric model without R-parity (RPV-MSSM), the third-generation enhanced left-right model and the axigluon model. We find that the polarization asymmetry may be enhanced to the accessible level in all these models while the correction to the spin correlation may be detectable in the axigluon model and the RPV-MSSM with $\lambda"$ couplings.Comment: Version in PRD (figs updated and discussions added

THE ENVIRONMENTAL EFFECTS OF FREEDOM TO FARM

The Federal Agriculture Improvement and Reform Act (FAIR) of 1996 ended commodity specific subsidies and resulted in a significant shift in corn and soybean production in 1997. While conservation compliance improved the environmental health of the Central U.S., changes in production due to the FAIR act have tempered these improvements.Agricultural and Food Policy, Environmental Economics and Policy,

Proliferation-dependent and cell cycle–regulated transcription of mouse pericentric heterochromatin

Pericentric heterochromatin transcription has been implicated in Schizosaccharomyces pombe heterochromatin assembly and maintenance. However, in mammalian systems, evidence for such transcription is inconsistent. We identify two populations of RNA polymerase II–dependent mouse γ satellite repeat sequence–derived transcripts from pericentric heterochromatin that accumulate at different times during the cell cycle. A small RNA species was synthesized exclusively during mitosis and rapidly eliminated during mitotic exit. A more abundant population of large, heterogeneous transcripts was induced late in G1 phase and their synthesis decreased during mid S phase, which is coincident with pericentric heterochromatin replication. In cells that lack the Suv39h1,2 methyltransferases responsible for H3K9 trimethylation, transcription occurs from more sites but is still cell cycle regulated. Transcription is not detected in quiescent cells and induction during G1 phase is sensitive to serum deprivation or the cyclin-dependent kinase inhibitor roscovatine. We demonstrate that mammalian pericentric heterochromatin transcription is linked to cellular proliferation. Our data also provide an explanation for inconsistencies in the detection of such transcripts in different systems