The abstraction transition taxonomy: developing desired learning outcomes through the lens of situated cognition

We report on a post-hoc analysis of introductory programming lecture materials. The purpose of this analysis is to identify what knowledge and skills we are asking students to acquire, as situated in the activity, tools, and culture of what programmers do and how they think. The specific materials analyzed are the 133 Peer Instruction questions used in lecture to support cognitive apprenticeship -- honoring the situated nature of knowledge. We propose an Abstraction Transition Taxonomy for classifying the kinds of knowing and practices we engage students in as we seek to apprentice them into the programming world. We find students are asked to answer questions expressed using three levels of abstraction: English, CS Speak, and Code. Moreover, many questions involve asking students to transition between levels of abstraction within the context of a computational problem. Finally, by applying our taxonomy in classifying a range of introductory programming exams, we find that summative assessments (including our own) tend to emphasize a small range of the skills fostered in students during the formative/apprenticeship phase

1026-85 Enhanced Defibrillation Efficacy with an Active Pectoral Pulse Generator

An active pectoral pulse generator can be incorporated in a single coil defibrillation lead system to achieve low defibrillation thresholds (DFT). However, the incremental benefit of an active pulse generator with an integrated lead system has not been evaluated. Accordingly, we performed a prospective trial of a 65 cc pulse generator shell with an Endotak lead in 22 consecutive pts undergoing defibrillator implantation. Energy (E) and leading edge voltage (V) at DFT was measured using a step down protocol to first failure with biphasic waveforms (60:40 tilt). Either lead alone (proximal coil = anode) or lead + shell (proximal coil and shell = anode) were tested with paired testing in random order.E(joules)V(volts)R(ohms)Lead alone13.1±6.7395±10549±5Lead + Shell8.5±3.1*319±61*42±4**p<0.001A DFT of≤10J was found in 50% (11/22) of patients with lead alone and 86% (19/22) of patients with lead + shell (p<0.02).In conclusion, adding an active pulse generator to an integrated transvenous lead significantly reduced DFTs and system impedance (R). The consistently low defibrillation energy requirements with the use of an active small pectoral shell, makes the development of a defibrillator with reduced size and lower maximal output feasible

Vibronic coupling in the superoxide anion: The vibrational dependence of the photoelectron angular distribution

We present a comprehensive photoelectron imaging study of the O₂(X³Σg⁻,v′=0–6)←O₂⁻(X²Πg,v′′=0) and O₂(a¹Δg,v′=0–4)←O₂⁻(X²Πg,v′′=0)photodetachment bands at wavelengths between 900 and 455 nm, examining the effect of vibronic coupling on the photoelectron angular distribution (PAD). This work extends the v′=1–4 data for detachment into the ground electronic state, presented in a recent communication [R. Mabbs, F. Mbaiwa, J. Wei, M. Van Duzor, S. T. Gibson, S. J. Cavanagh, and B. R. Lewis, Phys. Rev. A82, 011401–R (2010)]. Measured vibronic intensities are compared to Franck–Condon predictions and used as supporting evidence of vibronic coupling. The results are analyzed within the context of the one-electron, zero core contribution (ZCC) model [R. M. Stehman and S. B. Woo, Phys. Rev. A23, 2866 (1981)]. For both bands, the photoelectron anisotropy parameter variation with electron kinetic energy,β(E), displays the characteristics of photodetachment from a d-like orbital, consistent with the π∗g 2p highest occupied molecular orbital of O₂⁻. However, differences exist between the β(E) trends for detachment into different vibrational levels of the X³Σg⁻ and a ¹Δg electronic states of O₂. The ZCC model invokes vibrational channel specific “detachment orbitals” and attributes this behavior to coupling of the electronic and nuclear motion in the parent anion. The spatial extent of the model detachment orbital is dependent on the final state of O₂: the higher the neutral vibrational excitation, the larger the electron binding energy. Although vibronic coupling is ignored in most theoretical treatments of PADs in the direct photodetachment of molecular anions, the present findings clearly show that it can be important. These results represent a benchmark data set for a relatively simple system, upon which to base rigorous tests of more sophisticated models.The authors gratefully acknowledge support by the National Science Foundation Grant No. CHE-0748738 and ANU ARC Discovery Projects under Grant Nos. DP0666267 and DP0880850

Mollusks in the Northeastern Chukchi Sea

Infaunal and epifaunal mollusks of the northeastern Chukchi Sea were sampled and 139 molluscan taxa were identified. The pattern of spatial distribution of molluscan species was determined by cluster analysis, which resulted in six infaunal and five epifaunal station groups. Species characterizing various faunal groups are defined. Stepwise multiple discriminant analysis was applied to correlate benthic biological associations with environmental variables. Delineation of infaunal groups was mainly due to percentage of sand and bottom salinity, while epifaunal groups were separated by percent gravel and bottom temperature. An increase in abundance and biomass of infaunal mollusks occurred adjacent to and north and northwest of an identified bottom front between the Bering Shelf and Resident Chukchi Water and Alaska Coastal Water. Epifaunal molluscan abundance and biomass were highest near the coast. Mollusks, especially smaller species and the juvenile stages of larger species, represent a food resource for bottom-feeding predators in the study area.Key words: Chukchi Sea, mollusk, benthic, infauna, epifauna, bottom front, bottom-feeding predators, cluster analysis, discriminant analysisOn a fait un échantillonnage des mollusques de l'endofaune et de l'épifaune du nord-est de la mer des Tchouktches et on a identifié 139 taxons de mollusques. On a déterminé le schéma de répartition géographique des espèces de mollusques au moyen d'une analyse typologique, qui a donné six groupes de stations dans l'endofaune et cinq dans l'épifaune. On définit des espèces caractéristiques des divers groupes fauniques. On a appliqué une analyse discriminante multiple séquentielle pour corréler les associations biologiques du benthos aux variables de l'environnement. La délimitation des groupes de l'endofaune était due en grande partie au taux de sable et de salinité au fond, tandis que les groupes de l'épifaune étaient répartis en fonction du taux de gravier et de température au fond. Une augmentation dans la quantité et la biomasse des mollusques de l'endofaune apparaissait près du nord et du nord-ouest d'un front de fond compris entre le plateau continental, les eaux non brassées de la mer des Tchouktches et les eaux côtières de l'Alaska. C'est près de la côte qu'on retrouvait l'abondance et la biomasse maximales des mollusques de l'épifaune. Les mollusques, surtout ceux des petites espèces et ceux des grandes espèces qui étaient au stade juvénile, représentaient une source alimentaire pour les prédateurs benthiques vivant dans la zone d'étude.Mots clés : mer des Tchouktches, mollusque, benthique, enfofaune, épifaune, front au fond, prédateurs benthiques, analyse typologique, analyse discriminant

Health effects of the Federal Bureau of Prisons tobacco ban

BACKGROUND: Tobacco smoking remains the leading cause of preventable death in America, claiming 450,000 lives annually. Chronic Obstructive Pulmonary Disease, caused by smoking in the vast majority of cases, became the third leading cause of death in the U.S. in 2008. The burden of asthma, often exacerbated by tobacco exposure, has widespread clinical and public health impact. Despite this considerable harm, we know relatively little about the natural history of lung disease and respiratory impairment in adults, especially after smoking cessation. METHODS/DESIGN: Our paper describes the design and rationale for using the 2004 Federal Bureau of Prisons tobacco ban to obtain insights into the natural history of respiratory diseases in adult men and women of different races/ethnicities who are imprisoned in federal medical facilities. We have developed a longitudinal study of new prison arrivals, with data to be collected from each participant over the course of several years, through the use of standardized questionnaires, medical chart reviews, lung function tests, six-minute walk tests, and stored serum for the analysis of present and future biomarkers. Our endpoints include illness exacerbations, medication and health services utilization, lung function, serum biomarkers, and participants\u27 experience with their health and nicotine addiction. DISCUSSION: We believe the proposed longitudinal study will make a substantial contribution to the understanding and treatment of respiratory disease and tobacco addiction

Evidence for Grain Growth in Molecular Clouds: A Bayesian Examination of the Extinction Law in Perseus

We investigate the shape of the extinction law in two $1^{\circ}$ square fields of the Perseus molecular cloud complex. We combine deep red-optical (r, i and z band) observations obtained using Megacam on the MMT with UKIRT (United Kingdom Infrared Telescope) Infrared Deep Sky Survey near-infrared (J, H and K band) data to measure the colours of background stars. We develop a new hierarchical Bayesian statistical model, including measurement error, intrinsic colour variation, spectral type and dust reddening, to simultaneously infer parameters for individual stars and characteristics of the population. We implement an efficient Markov chain Monte Carlo algorithm utilizing generalized Gibbs sampling to compute coherent probabilistic inferences. We find a strong correlation between the extinction $(A_V)$ and the slope of the extinction law (parametrized by $R_V)$. Because the majority of the extinction towards our stars comes from the Perseus molecular cloud, we interpret this correlation as evidence of grain growth at moderate optical depths. The extinction law changes from the ‘diffuse’ value of $R_V \sim 3$ to the 'dense cloud' value of $R_V \sim 5$ as the column density rises from $A_V = 2$ to 10 mag. This relationship is similar for the two regions in our study, despite their different physical conditions, suggesting that dust grain growth is a fairly universal process.Astronom