Re-caching by Western scrub-jays (Aphelocoma californica) cannot be attributed to stress.

Western scrub-jays (Aphelocoma californica) live double lives, storing food for the future while raiding the stores of other birds. One tactic scrub-jays employ to protect stores is "re-caching"-relocating caches out of sight of would-be thieves. Recent computational modelling work suggests that re-caching might be mediated not by complex cognition, but by a combination of memory failure and stress. The "Stress Model" asserts that re-caching is a manifestation of a general drive to cache, rather than a desire to protect existing stores. Here, we present evidence strongly contradicting the central assumption of these models: that stress drives caching, irrespective of social context. In Experiment (i), we replicate the finding that scrub-jays preferentially relocate food they were watched hiding. In Experiment (ii) we find no evidence that stress increases caching. In light of our results, we argue that the Stress Model cannot account for scrub-jay re-caching

Performance Assessment of ESL and EFL Students

Thirteen prototypical performance tasks were selected from over 100 based on their generic appropriateness for the target population and on posited difficulty levels (associated with plus or niinus values for linguistic code command, cognitive operations, and communicative adaptation, as discussed in Norris, Brown, Hudson, & Yoshioka, 1998, after Skehan, 1996, 1998). These l3 tasks were used to create three test forms (with one anchor task common to all forms), two for use in an ESL setting at the University of Hawai'i, and one for use in an EFL setting at Kanda University of International Studies in Japan. In addition, two sets ofrating scales were created based on task-dependent and task-independent categories. For each individual task, the criteria for the task-dependent categories were created in consultation with an advanced language learner, a language teacher, and a non-ESL teacher, all ofwhom were well-acquainted with the target population and the prototype tasks. These criteria for success were allowed to differ from task to task depending on the input ofour consultants. The task-independent categories were created for each of three theoretically motivated components of task difficulty in terms of the adequacy of: (linguistic) code command, cognitive operations, and communicative adaptation. A third rating scale was developed for examinees to rate their own performance in terms of their familiarity with the task, their performance on the task, and the difficulty of the task. Pilot data were gathered from ESL and EFL students at a wide range of proficiency levels. Their performances were scored by raters using the task dependent and task-independent criteria. Analyses included descriptive statistics, reliability estimates (interrater, Cronbach alpha, etc.), correlational analysis, and implicational scale analysis. The results are interpreted and discussed in terms of: (a) the distributions ofscores for the task-dependent and task-independent ratings, (b) test reliability and ways to improve the consistency of measurement, and (c) test validify and the relationship of our task-based test to theory

Open-source development experiences in scientific software: the HANDE quantum Monte Carlo project

The HANDE quantum Monte Carlo project offers accessible stochastic algorithms for general use for scientists in the field of quantum chemistry. HANDE is an ambitious and general high-performance code developed by a geographically-dispersed team with a variety of backgrounds in computational science. In the course of preparing a public, open-source release, we have taken this opportunity to step back and look at what we have done and what we hope to do in the future. We pay particular attention to development processes, the approach taken to train students joining the project, and how a flat hierarchical structure aids communicationComment: 6 pages. Submission to WSSSPE

Concentration and δD of molecular hydrogen in boreal forests: Ecosystem-scale systematics of atmospheric H_2

We examined the concentration and δD of atmospheric H2 in a boreal forest in interior Alaska to investigate the systematics of high latitude soil uptake at ecosystem scale. Samples collected during nighttime inversions exhibited vigorous H_2 uptake, with concentration negatively correlated with the concentration of CO_2 (−0.8 to −1.2 ppb H_2 per ppm CO_2) and negatively correlated with δD of H_2. We derived H_2 deposition rates of between 2 to 12 nmol m^(−2) s^(−1). These rates are comparable to those observed in lower latitude ecosystems. We also derive an average fractionation factor, α = D:H_(residual)/D:H_(consumed) = 0.94 ± 0.01 and suggestive evidence that α depends on forest maturity. Our results show that high northern latitude soils are a significant sink of molecular hydrogen indicating that the record of atmospheric H_2 may be sensitive to changes in climate and land use

Canonical Melnikov theory for diffeomorphisms

We study perturbations of diffeomorphisms that have a saddle connection between a pair of normally hyperbolic invariant manifolds. We develop a first-order deformation calculus for invariant manifolds and show that a generalized Melnikov function or Melnikov displacement can be written in a canonical way. This function is defined to be a section of the normal bundle of the saddle connection. We show how our definition reproduces the classical methods of Poincar\'{e} and Melnikov and specializes to methods previously used for exact symplectic and volume-preserving maps. We use the method to detect the transverse intersection of stable and unstable manifolds and relate this intersection to the set of zeros of the Melnikov displacement.Comment: laTeX, 31 pages, 3 figure

SUMOylation of nuclear actin

Actin, a major component of the cytoplasm, is also abundant in the nucleus. Nuclear actin is involved in a variety of nuclear processes including transcription, chromatin remodeling, and intranuclear transport. Nevertheless, the regulation of nuclear actin by posttranslational modifications has not been investigated. We now show that nuclear actin is modified by SUMO2 and SUMO3 and that computational modeling and site-directed mutagenesis identified K68 and K284 as critical sites for SUMOylating actin. We also present a model for the actin–SUMO complex and show that SUMOylation is required for the nuclear localization of actin