GOVERNMENT POLICY, WIND EROSION, AND ECONOMIC VIABILITY IN SEMI-ARID AGRICULTURE: THE CASE OF THE SOUTHERN TEXAS HIGH PLAINS

The 1996 farm bill challenges agricultural producers to pursue conservation objectives while allowing flexibility and reducing subsidies. The nature of this challenge for semi-arid rainfed, wind-erosion-prone agriculture is explored via a behavioral model. Simulations of farm-firm decision making under scenarios in the southern Texas High Plains are evaluated. Results indicate that the removal of subsidies, while lowering farm incomes, does not, under most assumptions, alter cropping system choice. Alternatively, under a variety of assumptions, the imposition of an erosion tax shuts down cropping.Conservation practices, Cropping system choice, Economic dynamics, FAIR Act of 1996, Agricultural and Food Policy,

STEMteach: Preparing the Next Generation of Mathematics and Science Teachers

With an increasing demand for individuals prepared in Science, Technology, Engineering, and Mathematics (STEM), one university responded to this call by changing its teacher preparation program. Better-prepared mathematics and science teachers have the opportunity to engage and excite students, thereby preparing and promoting more of them to enter the STEM professions. The described program is a replication of the national UTeach model that recruits content majors in mathematics and science to explore the teaching profession during a first-semester course that includes an early field experience in the elementary grades. This field experience is designed to be engaging for both the teacher education candidates and the elementary students in an effort to demonstrate the joy of teaching and to retain the candidates in the program. The ultimate goal of the program is to increase the production of quality secondary mathematics and science teachers who can transfer their own deep understanding of their content to students so that these students will be career and college ready in the STEM disciplines

Modeling highly pathogenic avian influenza transmission in wild birds and poultry in West Bengal, India.

Wild birds are suspected to have played a role in highly pathogenic avian influenza (HPAI) H5N1 outbreaks in West Bengal. Cluster analysis showed that H5N1 was introduced in West Bengal at least 3 times between 2008 and 2010. We simulated the introduction of H5N1 by wild birds and their contact with poultry through a stochastic continuous-time mathematical model. Results showed that reducing contact between wild birds and domestic poultry, and increasing the culling rate of infected domestic poultry communities will reduce the probability of outbreaks. Poultry communities that shared habitat with wild birds or those indistricts with previous outbreaks were more likely to suffer an outbreak. These results indicate that wild birds can introduce HPAI to domestic poultry and that limiting their contact at shared habitats together with swift culling of infected domestic poultry can greatly reduce the likelihood of HPAI outbreaks

Nutritional support for head-injured patients

Copyright John Wiley & Sons. This review is published as a Cochrane Review in the Cochrane Database of Systematic Reviews 2004, Issue 3. Cochrane Reviews are regularly updated as new evidence emerges and in response to comments and criticisms, and the Cochrane Database of Systematic Reviews should be consulted for the most recent version of the Review.’ Perel, P. , Yanagawa, T. , Bunn, F. , Roberts, I. , Wentz, R. and Pierro, A. Nutritional support for head-injured patients. Cochrane Database of Systematic Reviews 2004, Issue 3. Art. No.: CD001530. DOI: 10.1002/14651858.CD001530.pub2Background: Head injury increases the body's metabolic responses, and therefore nutritional demands. Provision of an adequate supply of nutrients is associated with improved outcome. The best route for administering nutrition (parenterally (TPN) or enterally (EN)), and the best timing of administration (for example, early versus late) of nutrients needs to be established. Objectives: To quantify the effect on mortality and morbidity of alternative strategies of providing nutritional support following head injury. Search strategy: Trials were identified by computerised searches of the Cochrane Injuries Group specialised register, Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, National Research Register, Web of Science and other electronic trials registers. Reference lists of trials and review articles were checked. The searches were last updated in July 2006. Selection criteria: Randomised controlled trials of timing or route of nutritional support following acute traumatic brain injury. Data collection and analysis: Two authors independently abstracted data and assessed trial quality. Information was collected on death, disability, and incidence of infection. If trial quality was unclear, or if there were missing outcome data, trialists were contacted in an attempt to get further information. Main results: A total of 11 trials were included. Seven trials addressed the timing of support (early versus delayed), data on mortality were obtained for all seven trials (284 participants). The relative risk (RR) for death with early nutritional support was 0.67 (95% CI 0.41 to 1.07). Data on disability were available for three trials. The RR for death or disability at the end of follow-up was 0.75 (95% CI 0.50 to 1.11). Seven trials compared parenteral versus enteral nutrition. Because early support often involves parenteral nutrition, three of the trials are also included in the previous analyses. Five trials (207 participants) reported mortality. The RR for mortality at the end of follow-up period was 0.66 (0.41 to 1.07). Two trials provided data on death and disability. The RR was 0.69 (95% Cl 0.40 to 1.19). One trial compared gastric versus jejunal enteral nutrition, there were no deaths and the RR was not estimable. Authors' conclusions: This review suggests that early feeding may be associated with a trend towards better outcomes in terms of survival and disability. Further trials are required. These trials should report not only nutritional outcomes but also the effect on death and disability.Peer reviewe

A Stochastic Latent Moment Model for Electricity Price Formation

The wide range of models needed to support the various short-term operations for electricity generation demonstrates the importance of accurate specifications for the uncertainty in market prices. This is becoming increasingly challenging, since electricity hourly price densities exhibit a variety of shapes, with their characteristic features changing substantially within the day and over time, and the influx of renewable power, wind and solar in particular, has amplified these effects. A general-purpose, analytically tractable representation of the stochastic price formation process would have considerable value for operations control and trading, but existing empirical approaches for the application of standard density functions are unsatisfactory. We develop a general four parameter stochastic model for hourly prices, in which the four moments of the density function are dynamically estimated as latent state variables and furthermore modelled as functions of several plausible exogenous drivers. This provides a transparent and credible model that is suffciently flexible to capture the shape-shifting effects, particularly with respect to the wind and solar output variations causing dynamic switches in the upside and downside risks. Extensive testing on German wholesale price data, benchmarked against quantile regression and other models in out-of-sample backtesting, validated the approach and its analytical appeal

The Becklin-Neugebauer Object as a Runaway B Star, Ejected 4000 years ago from the theta^1C system

We attempt to explain the properties of the Becklin-Neugebauer (BN) object as a runaway B star, as originally proposed by Plambeck et al. (1995). This is one of the best-studied bright infrared sources, located in the Orion Nebula Cluster -- an important testing ground for massive star formation theories. From radio observations of BN's proper motion, we trace its trajectory back to Trapezium star theta^1C, the most massive (45 Msun) in the cluster and a relatively tight (17 AU) visual binary with a B star secondary. This origin would be the most recent known runaway B star ejection event, occurring only \~4000 yr ago and providing a unique test of models of ejection from multiple systems of massive stars. Although highly obscured, we can constrain BN's mass (~7 Msun) from both its bolometric luminosity and the recoil of theta^1C. Interaction of a runaway B star with dense ambient gas should produce a compact wind bow shock. We suggest that X-ray emission from this shocked gas may have been seen by Chandra: the offset from the radio position is ~300 AU in the direction of BN's motion. Given this model, we constrain the ambient density, wind mass-loss rate and wind velocity. BN made closest approach to the massive protostar, source ``I'', 500 yr ago. This may have triggered enhanced accretion and thus outflow, consistent with previous interpretations of the outflow being a recent (~10^3 yr) "explosive" event.Comment: 6 pages, accepted to ApJ Letter

Constraining f(R) Gravity as a Scalar Tensor Theory

We search for viable f(R) theories of gravity, making use of the equivalence between such theories and scalar-tensor gravity. We find that models can be made consistent with solar system constraints either by giving the scalar a high mass or by exploiting the so-called chameleon effect. However, in both cases, it appears likely that any late-time cosmic acceleration will be observationally indistinguishable from acceleration caused by a cosmological constant. We also explore further observational constraints from, e.g., big bang nucleosynthesis and inflation.Comment: 15 pages, 5 figure