Vertical movement patterns of skipjack tuna (Katsuwonus pelamis) in the eastern equatorial Pacific Ocean, as revealed with archival tags

Thirty-three skipjack tuna (Katsuwonus pelamis) (53−73 cm fork length) were caught and released with implanted archival tags in the eastern equatorial Pacific Ocean during April 2004. Six skipjack tuna were recap-tured, and 9.3 to 10.1 days of depth and temperature data were down-loaded from five recovered tags. The vertical habitat-use distributions indicated that skipjack tuna not associated with floating objects spent 98.6% of their time above the thermocline (depth=44 m) during the night, but spent 37.7% of their time below the thermocline during the day. When not associated with floating objects, skipjack tuna displayed repetitive bounce-diving behavior to depths between 50 and 300 m during the day. The deepest dive recorded was 596 m, where the ambient temperature was 7.7°C. One dive was particularly remarkable because the fish contin-uously swam for 2 hours below the thermocline to a maximum depth of 330 m. During that dive, the ambient temperature reached a low of 10.5°C, and the peritoneal cavity temperature reached a low of 15.9°C. The vertical movements and habitat use of skipjack tuna, revealed in this study, provide a much greater understanding of their ecological niche and catchability by purse-seine fisheries

The spin rate of pre-collapse stellar cores: wave-driven angular momentum transport in massive stars

The core rotation rates of massive stars have a substantial impact on the nature of core-collapse supernovae and their compact remnants. We demonstrate that internal gravity waves (IGW), excited via envelope convection during a red supergiant phase or during vigorous late time burning phases, can have a significant impact on the rotation rate of the pre-SN core. In typical ($10 \, M_\odot \lesssim M \lesssim 20 \, M_\odot$) supernova progenitors, IGW may substantially spin down the core, leading to iron core rotation periods $P_{\rm min,Fe} \gtrsim 30 \, {\rm s}$. Angular momentum (AM) conservation during the supernova would entail minimum NS rotation periods of $P_{\rm min,NS} \gtrsim 3 \, {\rm ms}$. In most cases, the combined effects of magnetic torques and IGW AM transport likely lead to substantially longer rotation periods. However, the stochastic influx of AM delivered by IGW during shell burning phases inevitably spin up a slowly rotating stellar core, leading to a maximum possible core rotation period. We estimate maximum iron core rotation periods of $P_{\rm max,Fe} \lesssim 5 \times 10^3 \, {\rm s}$ in typical core-collapse supernova progenitors, and a corresponding spin period of $P_{\rm max, NS} \lesssim 500 \, {\rm ms}$ for newborn neutron stars. This is comparable to the typical birth spin periods of most radio pulsars. Stochastic spin-up via IGW during shell O/Si burning may thus determine the initial rotation rate of most neutron stars. For a given progenitor, this theory predicts a Maxwellian distribution in pre-collapse core rotation frequency that is uncorrelated with the spin of the overlying envelope.Comment: Published in Ap

Interdistrict Choice and Teacher Beliefs: Implications for Educational Expectations, Equity, and Policymaking

Interdistrict choice, which allows families to choose between schools outside of their districts of residence, is currently serving more students than any other choice program in the United States. Yet, despite this popularity, there is a pressing need for more research on how interdistrict choice may affect educational equity within U.S. public schools. Drawing on the analytic framework of educational racial contract, this study examines the issue of teacher beliefs in the context of interdistrict choice at a large, urban high school in Arizona, where market-based school choice programs have been continually expanded for nearly three decades. Data were collected through a survey of 112 teachers, who rated their in- district and out-of-district students based on their perception of three developmental skill categories: 1) academic, 2) communication, and 3) behavior. Results speak to negative teacher beliefs about the educability of Students of Color and hold significant implications for teachers’ academic expectations, educational equity, and future policy decisions

Application of Social Cognitive Theory to the Study of Walking for Active Transportation

Active transportation (AT) is a form of physical activity involving human-powered transportation (e.g., walking) and is associated with health benefits. However, the majority of Canadians do not use AT. Although environmental factors, such as proximity, are correlated with AT, interventions to change such factors have been ineffective. According to social cognitive theory, both environmental and personal factors (i.e., social and spatial cognitions) may influence motivated behaviour. The social cognitions of interest in the present study included self-regulatory efficacy to schedule (i.e., confidence to regularly schedule walking for AT), and to overcome barriers (i.e., confidence to cope with barriers to walking for AT). Spatial cognitions included distance and travel time cognitions. The purpose of the study was to examine whether social cognitive personal factors (i.e., scheduling self-efficacy, barriers self-efficacy), spatial cognitive personal factors (i.e., distance and travel time cognitions), and an environmental factor (i.e., proximity) were associated with walking for AT to/from a university campus over a two-week period in a convenience sample of adults. Participants in this prospective observational study were a convenience sample of 105 students, faculty, and staff at a western Canadian university, who ranged in age from 17 to 55 years (M = 24.62 years, SD = 8.15). Participants completed three online surveys over a two-week period. Social cognitions for the following two-week period and spatial cognitions were assessed at Time 1. Recall of walking for AT to/from a university campus in the previous week was assessed at Time 2 and Time 3. Total walking for AT to/from campus over the two-week period was the outcome variable. The overall hierarchical multiple regression model predicting AT from the social and spatial cognitions and proximity was significant (R2adjusted = .53; p .05). Social cognitions, particularly self-regulatory efficacy to schedule, and efficacy to overcome barriers, may play an important role in individuals’ use of walking for AT to/from a university campus. Future research should continue to examine social cognitive-theory based personal and environmental predictors of AT, such as self-regulatory efficacy to goal set, outcome expectations, the weather and residential density, to better understand potential determinants of this health-promoting type of physical activity

Selective Information Processing of Body Size and Food Related Stimuli in Women Who Are Preoccupied With Body Size.

Overconcern or preoccupation with body size and weight is a central psychopathological feature of the eating disorders. The overconcern with body size is considered to be a function of fear of weight gain or fear of fatness . Cognitive theories of psychopathology have hypothesized that fear results in an increased activation of cognitive structures associated with the feared object. This increased activation (priming) is hypothesized to enhance the processing of information related to the feared object. This study tested this hypothesis using a lexical decision task. Individuals with extreme body size preoccupation were evaluated for a selective information processing of body size related words and food related words. Subjects with high body size preoccupation, i.e. a score of 110 or greater on the Body Shape Questionnaire (BSQ), correctly identified significantly more food and body words when compared to subjects with low concern about body size, i.e. a score of 50 or less on the BSQ. The groups did not differ on identification of control words. These results were interpreted as support for the anxiety model of eating disorders and cognitive theories of psychopathology

Tidally Induced Oscillations and Orbital Decay in Compact Triple-Star Systems

We investigate the nature of tidal effects in compact triple-star systems. The hierarchical structure of a triple system produces tidal forcing at high frequencies unobtainable in binary systems, allowing for the tidal excitation of high frequency p-modes in the stellar components. The tidal forcing exists even for circular, aligned, and synchronized systems. We calculate the magnitude and frequencies of three-body tidal forcing on the central primary star for circular and coplanar orbits, and we estimate the amplitude of the tidally excited oscillation modes. We also calculate the secular orbital changes induced by the tidally excited modes, and show that they can cause significant orbital decay. During certain phases of stellar evolution, the tidal dissipation may be greatly enhanced by resonance locking. We then compare our theory to observations of HD 181068, which is a hierarchical triply eclipsing star system in the Kepler field of view. The observed oscillation frequencies in HD 181068 can be naturally explained by three-body tidal effects. We then compare the observed oscillation amplitudes and phases in HD 181068 to our predictions, finding mostly good agreement. Finally, we discuss the past and future evolution of compact triple systems like HD 181068.Comment: 19 pages, 8 figures, published in MNRA

Movements, behavior, and habitat selection of bigeye tuna (Thunnus obesus) in the eastern equatorial Pacific, ascertained through archival tags

Ninety-six bigeye tuna (88– 134 cm fork length) were caught and released with implanted archival (electronic data storage) tags near fish-aggregating devices (FADs) in the equatorial eastern Pacific Ocean (EPO) during April 2000. Twenty-nine fish were recaptured, and the data from twenty-seven tags were successfully downloaded and processed. Time at liberty ranged from 8 to 446 days, and data for 23 fish at liberty for 30 days or more are presented. The accuracy in geolocation estimates, derived from the light level data, is about 2 degrees in latitude and 0.5 degrees in longitude in this region. The movement paths derived from the filtered geolocation estimates indicated that none of the fish traveled west of 110°W during the period between release and recapture. The null hypothesis that the movement path is random was rejected in 17 of the 22 statistical tests of the observed movement paths. The estimated mean velocity was 117 km/d. The fish exhibited occasional deep-diving behavior, and some dives exceeded 1000 m where temperatures were less than 3°C. Evaluations of timed depth records, resulted in the discrimination of three distinct behaviors: 54.3% of all days were classified as unassociated (with a floating object) type-1 behavior, 27.7% as unassociated type-2 behavior, and 18.7% as behavior associated with a floating object. The mean residence time at floating objects was 3.1 d. Data sets separated into day and night were used to evaluate diel differences in behavior and habitat selection. When the fish were exhibiting unassociated type-1 behavior (diel vertical migrations), they were mostly at depths of less than 50 m (within the mixed layer) throughout the night, and during the day between 200 and 300 m and 13° and 14°C. They shifted their average depths in conjunction with dawn and dusk events, presumably tracking the deep-scattering layer as a foraging strategy. There were also observed changes in the average nighttime depth distributions of the fish in relation to moon phase