Hedging in Field Theory Models of the Term Structure

We use path integrals to calculate hedge parameters and efficacy of hedging in a quantum field theory generalization of the Heath, Jarrow and Morton (HJM) term structure model which parsimoniously describes the evolution of imperfectly correlated forward rates. We also calculate, within the model specification, the effectiveness of hedging over finite periods of time. We use empirical estimates for the parameters of the model to show that a low dimensional hedge portfolio is quite effective.Comment: 18 figures, Invited Talk, International Econophysics Conference, Bali, 28-31 August 200

Delineating pattern and process in tropical lowland : mealy parrot migration dynamics as a guide for regional conservation planning

Most reserves fail to capture the habitat heterogeneity necessary to maintain viable populations of wide-ranging species. Methods to determine defensible dimensions of reserves and reserve networks are needed. The primary goal of this study was to develop such methods for lowland tropical forests by examining habitat- and spatial-use patterns of the Mealy Parrot (Amazona farinosa) in northern Guatemala. Regional connectivity has been demonstrated by altitudinal migration of birds that track seasonal fruit availability; it is now recognized that a suite of habitats along the elevational gradient must be protected to conserve biodiversity of tropical montane ecosystems. However, in tropical lowlands, little is known about spatiotemporal patterns of resources and animals that rely on them. I considered the large-bodied, frugivorous Mealy Parrot a useful focal species because its movements and habitat use should be coupled with the ecological factors determining fruit distribution. Individual- and population-based methods were developed in this study. In each of 4 years, radio telemetry revealed that adult Mealy Parrots breeding in northeastern Guatemala engaged in predictable seasonal migrations within mature lowland forest. Although the area covered by these parrots was considerable (10,000 km²), more significant was the consistency of their movements and specific locations utilized. Canopy-based population surveys were used to estimate densities of all 6 locally occurring parrot species as a function of landscape type and season over a two-year period; the data suggest that migration is common in this parrot community. Mealy Parrots rely on mature lowland forest arrayed along regional environmental gradients. Over distances of a few hundred kilometers and a range in elevation of [approximately] 200 m, variation in fruiting phenology, forest composition, and rainfall shape this species' movement patterns. Basing reserve design on size alone is insufficient. Large protected areas, such as the 600 km² Tikal National Park and even the 21,000 km² Maya Biosphere Reserve, will not maintain this population of Mealy Parrots without inclusion of areas that encompass the range of spatiotemporal variability governing migration patterns. The Mealy Parrot occurs from Mexico through Amazonia and may serve as a valuable focal species for conservation planning in other parts of its range

AN INDIVIDUALIZED MARKING SCHEME FOR SANDHILL CRANES AND ITS USE TO DETERMINE FALL MIGRATION INTERVAL

A color-band based marking scheme was used for individually marking sa ndhill cranes in Florida. The band-loss rate was 2.8% per year between 1977 and 1988. Band loss was greatest on bands placed below the ankle joint and occurred most frequently during years 2 to 5. Color-marked individuals monitored during fall migration averaged 6.2 days (r=5-13 days) between the Jasper-Pulaski Fish and Wildlife area in northwestern Indiana and winlering areas in northern Florida

Adolescents, Adults and Rewards: Comparing Motivational Neurocircuitry Recruitment Using fMRI

Background: Adolescent risk-taking, including behaviors resulting in injury or death, has been attributed in part to maturational differences in mesolimbic incentive-motivational neurocircuitry, including ostensible oversensitivity of the nucleus accumbens (NAcc) to rewards. Methodology/Principal Findings: To test whether adolescents showed increased NAcc activation by cues for rewards, or by delivery of rewards, we scanned 24 adolescents (age 12–17) and 24 adults age (22–42) with functional magnetic resonance imaging while they performed a monetary incentive delay (MID) task. The MID task was configured to temporally disentangle potential reward or potential loss anticipation-related brain signal from reward or loss notification-related signal. Subjects saw cues signaling opportunities to win or avoid losing $0,$.50, or $5 for responding quickly to a subsequent target. Subjects then viewed feedback of their trial success after a variable interval from cue presentation of between 6 to17 s. Adolescents showed reduced NAcc recruitment by reward-predictive cues compared to adult controls in a linear contrast with non-incentive cues, and in a volume-of-interest analysis of signal change in the NAcc. In contrast, adolescents showed little difference in striatal and frontocortical responsiveness to reward deliveries compared to adults. Conclusions/Significance: In light of divergent developmental difference findings between neuroimaging incentive paradigms (as well as at different stages within the same task), these data suggest that maturational differences i

The ACS LCID project IV: detection of the RGB bump in isolated galaxies of the Local Group

We report the detection and analysis of the red giant branch luminosity function bump in a sample of isolated dwarf galaxies in the Local Group. We have designed a new analysis approach comparing the observed color-magnitude diagrams with theoretical best-fit color-magnitude diagrams derived from precise estimates of the star formation histories of each galaxy. This analysis is based on studying the difference between the V-magnitude of the RGB bump and the horizontal branch at the level of the RR Lyrae instability strip (Delta_vhbb) and we discuss here a technique for reliably measuring this quantity in complex stellar systems. By using this approach, we find that the difference between the observed and predicted values of Delta_vhbb is +0.13 +/- 0.14 mag. This is smaller, by about a factor of two, than the well-known discrepancy between theory and observation at low metallicity commonly derived for Galactic globular clusters. This result is confirmed by a comparison between the adopted theoretical framework and empirical estimates of the Delta_vhbb parameter for both a large database of Galactic globular clusters and for four other dSph galaxies for which this estimate is available in the literature. We also investigate the strength of the red giant branch bump feature (R_bump), and find very good agreement between the observed and theoretically predicted R_bump values. This agreement supports the reliability of the evolutionary lifetimes predicted by theoretical models of the evolution of low-mass stars.Comment: Accepted for publication on Ap

Auditory but Not Audiovisual Cues Lead to Higher Neural Sensitivity to the Statistical Regularities of an Unfamiliar Musical Style

It is still a matter of debate whether visual aids improve learning of music. In a multisession study, we investigated the neural signatures of novel music sequence learning with or without aids (auditory-only: AO, audiovisual: AV). During three training sessions on 3 separate days, participants (nonmusicians) reproduced (note by note on a keyboard) melodic sequences generated by an artificial musical grammar. The AV group (n = 20) had each note color-coded on screen, whereas the AO group (n = 20) had no color indication. We evaluated learning of the statistical regularities of the novel music grammar before and after training by presenting melodies ending on correct or incorrect notes and by asking participants to judge the correctness and surprisal of the final note, while EEG was recorded. We found that participants successfully learned the new grammar. Although the AV group, as compared to the AO group, reproduced longer sequences during training, there was no significant difference in learning between groups. At the neural level, after training, the AO group showed a larger N100 response to lowprobability compared to high-probability notes, suggesting an increased neural sensitivity to statistical properties of the grammar; this effect was not observed in the AV group. Our findings indicate that visual aids might improve sequence reproduction while not necessarily promoting better learning, indicating a potential dissociation between sequence reproduction and learning. We suggest that the difficulty induced by auditory-only input during music training might enhance cognitive engagement, thereby improving neural sensitivity to the underlying statistical properties of the learned material