Contra Epstein, Good Explanations Predict

Epstein has argued that an explanation\'s capacity to make predictions should play a minor role in its evaluation . This view contradicts centuries of scientific practice and, at least, decades of philosophy of science. We argue that the view is not only unfounded but seems to arise from a mistaken fear that ABM models are in need of defense against the criticism that they don\'t necessarily forecast events in the natural or social world.ABM, Agent Based Model, Modeling, Prediction, Explanation, Philosophy of Science

The emergence of insect resistance in Bt-corn: implication of resistance management information under uncertainty

"The successful management of transgenic technology is likely to depend on the economic behavioral response of farmers to the regulated use of transgenic crops. A well-studied example is the widespread use of Bt-corn, in the United States, and elsewhere, to control the European Corn Borer, a major corn pest. The extensive use of Bt-corn has led to concerns about the emergence of insect resistance. The United States Environment Protection Agency addressed this potential problem by developing an insect resistance management strategy, based, in part, on complex mathematical models using detailed biological assumptions about the population genetics and life history of the European Corn Borer. However, seed companies and others have sometimes used simpler deterministic profit models to justify the economics of Bt-corn to potential growers. Therefore an over reliance, by regulatory agencies, on complex modeling approaches may obscure the likely economic behavioral response of farmers who rely on these less complex models. However, the determinants of adoption are numerous, profit being one of them. We develop a simple model for the spread of resistance based on the logistic growth equation and use it to investigate the effect of uncertainty on farmer decisions to plant Bt-corn and follow EPA management rules. The model results suggest that planting Bt-corn is an optimal strategy under the type of uncertainty assumed in the model and that short-term economic behavior is likely to lead to the Environment Protection Agency management rules not being followed. Our results add weight to existing work on this problem." Authors' AbstractBt-corn, logistic growth, Monte Carlo methods, Corn, Environmental protection, Economics Methodology,

“The Friend Zone”- friendship moderates the impact of a web-based group dynamics application on group cohesion: a randomized trial

Master of Public HealthDepartment of KinesiologyBrandon IrwinPurpose: Face-to-face group dynamics-based (GDB) programs have been shown to be effective in promoting group cohesion and physical activity (PA). Recent evidence suggests that GDB principles can be successfully translated to web-based applications to impact group cohesion. The social nature of such applications allows for interactions to occur between friends and strangers alike, potentially moderating the effects of such GDB applications. Optimal group composition within GDB web applications has yet to be determined. The present study examines the moderating effects of group composition in a GDB application on group cohesion and PA. Methods: Participants (n = 166) were randomized into same-sex pairs and then randomly assigned to an experimental condition: stranger (no app), stranger (using app), friend (using app) or individual control. Participants in all conditions performed two sets of planking exercises. In between sets, those in partnered conditions interacted with their partner using a GDB social media app, where they participated in a series of team-building activities. The main dependent variables were group cohesion and physical activity, calculated as the total persistence during Block 2, controlling for Block 1 persistence. Results: Results indicate that the group integration dimensions of cohesion were higher in groups that used the application than those that did not (GI-T: p= .001; GI-S: p= .004). Friends that used the app reported greater cohesion across all dimensions than strangers that did the same (ATG-T: p= .006; ATG-S: p= .003; GI-T: p= .001; GI-S: p< .001). There was also a significant difference in PA (p=.004) between the two app-using conditions. However, there was no significant difference in PA between app using conditions and strangers that did not use the app (p= .495). Conclusions: Group cohesion can be enhanced through the use of an online GDB application. Using an online GDB application with a friend is associated with higher levels of cohesion. Further research is necessary to identify effective online GDB applications for impacting physical activity and cohesion in field settings

The future of biofuel (panel discussion)

Biomass energy - United States ; Environmental policy

Consensual Qualitative Research: An Update

The authors reviewed the application of consensual qualitative research (CQR) in 27 studies published since the method’s introduction to the field in 1997 by C. E. Hill, B. J. Thompson, and E. N. Williams (1997). After first describing the core components and the philosophical underpinnings of CQR, the authors examined how it has been applied in terms of the consensus process, biases, research teams, data collection, data analysis, and writing up the results and discussion sections of articles. On the basis of problems that have arisen in each of these areas, the authors made recommendations for modifications of the method. The authors concluded that CQR is a viable qualitative method and suggest several ideas for research on the method itself

CTQ 839: Candidate for the Smallest Projected Separation Binary Quasar

We report the discovery of the new double quasar CTQ 839. This B = 18.3, radio quiet quasar pair is separated by 2.1" in BRIH filters with magnitude differences of delta m_B = 2.5, delta m_R = delta m_I = 1.9, and delta m_H = 2.3. Spectral observations reveal both components to be z = 2.24 quasars, with relative redshifts that agree at the 100 km/s level, but exhibit pronounced differences in the equivalent widths of related emission features, as well as an enhancement of blue continuum flux in the brighter component longward of the Ly alpha emission feature. In general, similar redshift double quasars can be the result of a physical binary pair, or a single quasar multiply imaged by gravitational lensing. Empirical PSF subtraction of R and H band images of CTQ 839 reveal no indication of a lensing galaxy, and place a detection limit of R = 22.5 and H = 17.4 for a third component in the system. For an Einstein-de Sitter cosmology and SIS model, the R band detection limit constrains the characteristics of any lensing galaxy to z_lens >= 1 with a corresponding luminosity of L >~ 5 L_*, while an analysis based on the redshift probability distribution for the lensing galaxy argues against the existence of a z_lens >~ 1 lens at the 2 sigma level. A similar analysis for a Lambda dominated cosmology, however, does not significantly constrain the existence of any lensing galaxy. The broadband flux differences, spectral dissimilarities, and failure to detect a lensing galaxy make the lensing hypothesis for CTQ 839 unlikely. The similar redshifts of the two components would then argue for a physical quasar binary. At a projected separation of 8.3/h kpc (Omega_matter = 1), CTQ 839 would be the smallest projected separation binary quasar currently known.Comment: Latex, 23 pages including 5 ps figures; accepted for publication in A

An AGN Identification for 3EG J2006-2321

We present a multiwavelength analysis of the high-energy gamma-ray source 3EG J2006-2321. The flux of this source above 100 MeV is shown to be variable on time scales of days and months. Optical observations and careful examination of archived radio data indicate that its radio counterpart is PMN J2005-2310, a flat-spectrum radio quasar with a 5-GHz flux density of 260 mJy. Study of the $V=18.7$ optical counterpart indicates a redshift of 0.833 and variable linear polarization. No X-ray source has been detected near the position of PMN J2005-2310, but an X-ray upper limit is derived from ROSAT data. This upper limit provides for a spectral energy distribution with global characteristics similar to those of known gamma-ray blazars. Taken together, these data indicate that 3EG J2006-2321, listed as unidentified in the 3rd EGRET Catalog, is a member of the blazar class of AGN. The 5-GHz radio flux density of this blazar is the lowest of the 68 EGRET-detected AGN. The fact that EGRET has detected such a source has implications for unidentified EGRET sources, particularly those at high latitudes ($|b|>30^{\circ}$), many of which may be blazars.Comment: 22 pages, 6 figures. To appear in ApJ v569 n1, 10 April 200