Movements of Channel Catfish and Flathead Catfish in Beaver Reservoir, Northwest Arkansas

A total of 497 channel catfish, Ictalurus punctatus, and flathead catfish, Pylodictis olivaris. were tagged in Beaver Reservoir during two November-April tagging periods (1967-68 and 1968-69); total recaptures were 9.5 and 11.7% respectively. The longest time between tagging and recapture was 1622 days (4.4 years) for channel catfish and 494 days (1.4 years) for flathead catfish. The longest distances traveled were 43.1 km by a channel catfish and 44.3 km by a flathead catfish. Fisherman returns indicated that catfish were caught primarily from April through July. The many recaptures, even after long periods, within 1.6 km of the tagging point, suggested that fish moved little, or had homing tendencies. Captures of fish in trap nets indicated that rainfall and inflow possibly stimulated movements of channel catfish during the winter and early spring

String Breaking in Four Dimensional Lattice QCD

Virtual quark pair screening leads to breaking of the string between fundamental representation quarks in QCD. For unquenched four dimensional lattice QCD, this (so far elusive) phenomenon is studied using the recently developed truncated determinant algorithm (TDA). The dynamical configurations were generated on an Athlon 650 MHz PC. Quark eigenmodes up to 420 MeV are included exactly in these TDA studies performed at low quark mass on large coarse (but O($a^2$) improved) lattices. A study of Wilson line correlators in Coulomb gauge extracted from an ensemble of 1000 two-flavor dynamical configurations reveals evidence for flattening of the string tension at distances R $\geq$ approximately 1 fm.Comment: 16 pages, 5 figures, Latex (deleted extraneous eps figure file

INFORMATION SOURCES PREFERRED BY LIMITED RESOURCE FARMERS IN USING AGRICULTURAL RISK TOOLS

The paper examines limited resource farmers' perceptions of the usefulness of selected sources of risk management information. The rationale is to understand the information needs of this group of farmers and to customize outreach programs to address their needs.Risk and Uncertainty,

Distributed Scaffolding: Wiki Collaboration Among Latino High School Chemistry Students

The primary purpose of this study was to evaluate if wiki collaboration among Latino high school chemistry students can help reduce the science achievement gap between Latino and White students. The study was a quasi-experimental pre/post control group mixed-methods design. It used three intact sections of a high school chemistry course. The first research question asked if there is a difference in academic achievement between a treatment and control group on selected concepts from the topics of bonding, physical changes, and chemical changes, when Latino high school chemistry students collaborate on a quasi-natural wiki project. Overall results for all three activities (Bonding, Physical Changes, and Chemical Changes) indicated no significant difference between the wiki and control group. However, students performing the chemical changes activity did significantly better than their respective control group. Furthermore, there was a significant association, with large effect size, between group membership and ability to overcome the misconception that aqueous ionic reactants in precipitation reactions exist as molecular pairs of ions. Qualitative analysis of classroom and computer lab dialogue, discussion board communication, student focus groups, teacher interviews, and wiki content attributes the better performance of the chemical changes wiki group to favorable differences in intersubjectivity and calibrated assistance, as well as learning about submicroscopic representations of precipitation reactions in multiple contexts. Furthermore, the nonsignificant result overall points to an aversion to peer editing as a possible cause. Drawing considerably on Vygotsky and Piaget, the results are discussed within the context of how distributed scaffolding facilitated medium levels of cognitive conflict. The second research question asked what the characteristics of distributed metacognitive scaffolding are when Latino high school chemistry students collaborate on a quasi-natural wiki project. Results suggested a higher frequency of metacognitive scaffolding by the teacher, over peers, for content knowledge and making connections knowledge. Teacher metacognitive scaffolding often took the form of posting discussion board questions designed to stimulate student reflection on their content or creativity. On the other hand, both teacher and peer metacognitive scaffolding for general goals knowledge and strategy knowledge was relatively infrequent. Recommendations are offered for improving teacher and peer metacognitive scaffolding

Heuristic Refinement Method for the Derivation of Protein Solution Structures: Validation on Cytochrome B562

A method is described for determining the family of protein structures compatible with solution data obtained primarily from nuclear magnetic resonance (NMR) spectroscopy. Starting with all possible conformations, the method systematically excludes conformations until the remaining structures are only those compatible with the data. The apparent computational intractability of this approach is reduced by assembling the protein in pieces, by considering the protein at several levels of abstraction, by utilizing constraint satisfaction methods to consider only a few atoms at a time, and by utilizing artificial intelligence methods of heuristic control to decide which actions will exclude the most conformations. Example results are presented for simulated NMR data from the known crystal structure of cytochrome b562 (103 residues). For 10 sample backbones an average root-mean-square deviation from the crystal of 4.1 A was found for all alpha-carbon atoms and 2.8 A for helix alpha-carbons alone. The 10 backbones define the family of all structures compatible with the data and provide nearly correct starting structures for adjustment by any of the current structure determination methods