Local Environment Control and Institutional Crowding-out

Regulations that are designed to improve social welfare typically begin with the premise that individuals are purely self-interested. Experimental evidence shows, however, that individuals do not typically behave this way; instead, they tend to strike a balance between self and group interests. From experiments performed in rural Colombia, we found that a regulatory solution for an environmental dilemma that standard theory predicts would improve social welfare clearly did not. This occurred because individuals confronted with the regulation began to exhibit less other-regarding behavior and made choices that were more self-interested; that is, the regulation appeared to crowd out other-regarding behavior.institutional crowding-out, external regulation, local environment quality, experiments, South America, Colombia

Economic inequality and burden-sharing in the provision of local environmental quality

A large, but inconclusive, literature addresses how economic heterogeneity affects the use of local resources and local environmental quality. One line of thought, which derives from Nash equilibrium provision of public goods, suggests that in contexts in which individual actions degrade local environmental quality, wealthier people in a community will tend to do more to protect environmental quality. In this paper we report on experiments performed in rural Colombia that were designed to explore the role that economic inequality plays in the å¢rovision-of local environmental quality. Subjects were asked to decide how much time to devote to collecting firewood from a local forest, which degrades local water quality, and how much to unrelated pursuits. Economic heterogeneity was introduced by varying the private returns to these alternative pursuits. Consistent with the Nash equilibrium prediction, we found that the players with more valuable alternative options put less pressure on local water quality. However, the subjects with less valuable alternative options showed significantly more restraint relative to their pure Nash strategies. Furthermore, they were willing to bear significantly greater opportunity costs to move their groups to outcomes that yielded higher average payoffs and better water quality than the Nash equilibrium outcome.Local environment quality, burden sharing, economic inequality, experiments

Correlated photon pairs generated from a warm atomic ensemble

We present measurements of the cross-correlation function of photon pairs at 780 nm and 1367 nm, generated in a hot rubidium vapor cell. The temporal character of the biphoton is determined by the dispersive properties of the medium where the pair generation takes place. We show that short correlation times occur for optically thick samples, which can be understood in terms of off-resonant pair generation. By modifying the linear response of the sample, we produce near-resonant photon pairs, which could in principle be used for entanglement distribution

Personality Variation in Little Brown Bats

Animal personality or temperament refers to individual differences in behaviour that are repeatable over time and across contexts. Personality has been linked to life-history traits, energetic traits and fitness, with implications for the evolution of behaviour. Personality has been quantified for a range of taxa (e.g., fish, songbirds, small mammals) but, so far, there has been little work on personality in bats, despite their diversity and potential as a model taxon for comparative studies. We used a novel environment test to quantify personality in little brown bats (Myotis lucifugus) and assess the short-term repeatability of a range of behaviours. We tested the hypothesis that development influences values of personality traits and predicted that trait values associated with activity would increase between newly volant, pre-weaning young-of-the-year (YOY) and more mature, self-sufficient YOY. We identified personality dimensions that were consistent with past studies of other taxa and found that these traits were repeatable over a 24-hour period. Consistent with our prediction, older YOY captured at a fall swarming site prior to hibernation had higher activity scores than younger YOY bats captured at a maternity colony, suggesting that personality traits vary as development progresses in YOY bats. Thus, we found evidence of short-term consistency of personality within individuals but with the potential for temporal flexibility of traits, depending on age."Funding was provided by a Natural Sciences and Engineering Research Council (NSERC) Canada Graduate Scholarship to AKM and post-doctoral fellowship to LPM as well as grants to CKRW from NSERC, the Canada Foundation for Innovation, the Manitoba Research and Innovation Fund and Manitoba Hydro Forest Enhancement Program."https://journals.plos.org/plosone/article?id=10.1371/journal.pone.008023

Fracture Characterization from Scattered Energy: A Case Study

We use 3D surface seismic data to determine the presence and the preferred orientation of fracture corridors in a field. The Scattering Index method is proving to be a robust tool for detecting and mapping fracture corridors. Fracture corridors largely control permeability and fluid flow in some fractured reservoirs. To apply the Scattering Index method, we compute the scattering transfer functions from the reservoir interval using prestack migrated data collected in four azimuth sectors. By measuring the azimuthal differences in the amount of scattering, we obtain maps of density of fracture corridors and their orientation across the survey area. We use geostatistical filtering to improve the spatial correlation of scattering index maps. The distribution and orientation of the final fracture corridors are interpreted considering the structure, fault network, and stress information. In the field, we observe several regions of high fracturing near the anticline’s crest and on its steepest slopes, on the southwest flank. Around well locations, fractures are oriented to the NW and NNW, which agrees with estimates of maximum stress direction from well data.Massachusetts Institute of Technology. Earth Resources Laborator

Crack Front Waves and the dynamics of a rapidly moving crack

Crack front waves are localized waves that propagate along the leading edge of a crack. They are generated by the interaction of a crack with a localized material inhomogeneity. We show that front waves are nonlinear entities that transport energy, generate surface structure and lead to localized velocity fluctuations. Their existence locally imparts inertia, which is not incorporated in current theories of fracture, to initially "massless" cracks. This, coupled to crack instabilities, yields both inhomogeneity and scaling behavior within fracture surface structure.Comment: Embedded Latex file including 4 figure

Analysis of Scattered Signal to Estimate Reservoir Fracture Parameters

We detect fracture corridors and determine their orientation and average spacing based on an analysis of seismic coda in the frequency-wave number (f-k ) domain. Fracture corridors have dimensions similar to seismic wavelengths which causes scattering. The distribution of energy in shot records in the f-k domain depends upon the orientation of the records relative to the fracture strike. In the direction normal to fractures, scattered waves propagate with slower apparent velocities than waves propagating along the fracture channels. The associated f-k spectral differences allow the identification of the preferred fracture orientation and spacing. We apply our technique to a fractured reservoir in the Lynx field, in the Canadian foothills. The estimated preferential fracture orientation is about N40 E, which agrees with regional stress measurements. The average fracture spacing is 75 m on the West side of the survey, while fractures are more sparse on the East side. We also apply the Scattering Index methodology (Willis et al., 2006) to the same data, post-stack and pre-stack. This technique has higher resolution to map fracture distribution, intensity and orientation, and therefore complements the spectral method in providing an integrated description of reservoir fractures.United States. Dept. of Energy (award number DE-FC26-06NT42956)Massachusetts Institute of Technology. Earth Resources Laborator

Sensitivity of time lapse seismic data to the compliance of hydraulic fractures

We study the sensitivity of seismic waves to changes in the fracture normal and tangential compliances by analyzing the fracture sensitivity wave equation, which is derived by differentiating the elastic wave equation with respect to the fracture compliance. The sources for the sensitivity wavefield are the sensitivity moments, which are functions of fracture compliance, background elastic properties and the stress acting on the fracture surface. Based on the analysis of the fracture sensitivity wave equation, we give the condition for the weak scattering approximation to be valid for fracture scattering. Under the weak scattering approximation, we find that the percentage change of fracture compliance in hydraulic fracturing is equal to the percentage change of the recorded time-lapse seismic data. This could provide a means for monitoring the opening/closing of fractures in hydraulic fracturing through time-lapse seismic surveys.Eni-MIT Energy Initiative Founding Member Progra

The association between seafood intake and fecundability: Analysis from two prospective studies

Background: Seafood is an important source of omega\u20103 fatty acids, which have been associated with improved oocyte quality and embryo morphology in some studies. However, seafood is also a source of persistent organic pollutants and heavy metals, which may adversely affect fecundity. Previous studies of seafood intake and fecundity have generated inconsistent results. Methods: In two prospective cohort studies of 7836 female pregnancy planners from Denmark (Snart Foraeldre, n = 2709) and North America (PRESTO, n = 5127), we evaluated the association of dietary intake of total seafood and marine\u2010sourced long\u2010chain omega\u20103 fatty acids (eicosapentaenoic acid, docosahexaenoic acid, and docosapentaenoic acid) with fecundability. Participants completed a baseline questionnaire on sociodemographics, behavioral factors, anthropometrics, and medical history, and a food frequency questionnaire. Pregnancy status was updated bimonthly for up to 12 months or until reported conception. We estimated fecundability ratios (FRs) and 95% confidence intervals (CIs) using proportional probabilities regression models, adjusted for energy intake and other potential confounders. We restricted analyses to women with 646 menstrual cycles of attempt time at enrollment. Results: Intake of total seafood or marine\u2010sourced long\u2010chain omega\u20103 fatty acids was not appreciably associated with fecundability in either cohort ( 65200 vs. <50 g/week total seafood: FR = 0.94, 95% CI: 0.79\u20131.10 in Snart Foraeldre; FR = 1.00, 95% CI: 0.90\u20131.13 in PRESTO; marine fatty acids: 6590th vs. <25th percentile: FR = 1.00, 95% CI: 0.85\u20131.18 in Snart Foraeldre; FR = 0.97, 95% CI: 0.86\u20131.09 in PRESTO). In PRESTO, where we collected additional data on seafood preparation, we observed an inverse association between fecundability and fried shellfish ( 6510 g/week vs. none: FR = 0.77, 95% CI: 0.61\u20130.98), but not unfried shellfish ( 6520 g/week vs. none: FR = 0.98, 95% CI: 0.89\u20131.07); in Snart Foraeldre, there was no association with total shellfish intake. Conclusions: We found little association between seafood intake and fecundability overall, but greater intake of fried shellfish was associated with reduced fecundability among North American participants