The Effect of self-controlled practice on forearm passing, motivation, and affect in women’s volleyball players

Motor learning research has suggested that self-controlled practice (or “autonomy”) leads to more effective learning of motor tasks. Debate continues, however, as to why. Most motor behaviorists maintain the better learning is due to cognitive and information-processing factors. Recently, others have proposed the learning enhancement is due to such psychological factors as motivation and affect. The present study sought to measure motor skill learning, intrinsic motivation, and affect in self-controlled versus externally-controlled (yoked) practice conditions. Participants, 16 collegiate women’s volleyball student-athletes from two National Collegiate Athletic Association Division I programs, were paired by forearm passing skill level, and one of each pair was randomly placed in either the self-control or yoked group. The self-control participants were asked to design their own forearm passing drill during the practice phase of the experiment. The yoked participants followed the design established by the self-control participant to whom they were yoked. Each of the participants’ forearm passing accuracy was measured in a free ball passing drill consisting of a pre-test and practice phase on Day 1, and a post-test on Day 2. Their intrinsic motivation was measured using the Intrinsic Motivation Inventory (IMI), and their positive and negative affect was measured using the Positive and Negative Affect Scale – Expanded Edition (PANAS-X). The IMI and PANAS-X were administered in a baseline condition (after a team practice one week prior to participation in the study) at the end of Day 1, and the end of Day 2. Analysis of the data revealed no statistically significant differences between groups in either forearm passing, intrinsic motivation, or affect. Further research is needed to determine if intrinsic motivation and affect are partially responsible for the learning benefits of self-controlled practice

Can the James Webb Space Telescope detect isolated population III stars?

Isolated population III stars are postulated to exist at approximately z=10-30 and may attain masses up to a few hundred solar masses. The James Webb Space telescope (JWST) is the next large space based infrared telescope and is scheduled for launch in 2014. Using a 6.5 meter primary mirror, it will probably be able to detect some of the first galaxies forming in the early Universe. A natural question is whether it will also be able to see any isolated population III stars. Here, we calculate the apparent broadband AB-magnitudes for 300 solar masses population III stars in JWST filters at z=10-20. Our calculations are based on realistic stellar atmospheres and take into account the potential flux contribution from the surrounding HII region. The gravitational magnification boost achieved when pointing JWST through a foreground galaxy cluster is also considered. Using this machinery, we derive the conditions required for JWST to be able to detect population III stars in isolation. We find that a detection of individual population III stars with JWST is unlikely at these redshifts. However, the main problem is not necessarily that these stars are too faint, once gravitational lensing is taken into account, but that their surface number densities are too low.Comment: 6 pages, 3 figures, proceedings of CRF2010, DESY Hamburg, Nov 9-12 201

Does GPS supervision of intimate partner violence defendants reduce pretrial misconduct? Evidence from a quasi-experimental study

Objectives This research examines the effect global positioning system (GPS) technology supervision has on pretrial misconduct for defendants facing intimate partner violence charges. Methods Drawing on data from one pretrial services division, a retrospective quasi-experimental design was constructed to examine failure to appear to court, failure to appear to meetings with pretrial services, and rearrest outcomes between defendants ordered to pretrial GPS supervision and a comparison group of defendants ordered to pretrial supervision without the use of monitoring technology. Cox regression models were used to assess differences between quasi-experimental conditions. To enhance internal validity and mitigate model dependence, we utilized and compared results across four counterfactual comparison groups (propensity score matching, Mahalanobis distance matching, inverse probability of treatment weighting, and marginal mean weighting through stratification). Results Pretrial GPS supervision was no more or less effective than traditional, non-technology based pretrial supervision in reducing the risk of failure to appear to court or the risk of rearrest. GPS supervision did reduce the risk of failing to appear to meetings with pretrial services staff. Conclusions The results suggest that GPS supervision may hold untapped case management benefits for pretrial probation officers, a pragmatic focus that may be overshadowed by efforts to mitigate the risk of pretrial misconduct. Further, the results contribute to ongoing discussions on bail reform, pretrial practice, and the movement to reduce local jail populations. Although the cost savings are not entirely clear, relatively higher risk defendants can be managed in the community and produce outcomes that are comparable to other defendants. The results also call into question the ability of matching procedures to construct appropriate counterfactuals in an era where risk assessment informs criminal justice decision-making. Weighting techniques outperformed matching strategies

BIN Models for Trade-by-Trade Data. Modelling the Number of Trades in a Fixed Interval of Time

In this paper we propose a simple time series model of the number of transactions made in intervals of length $\Delta$ seconds. We call this model the {\sf BIN} model. The properties of the {\sf BIN} model are evaluated while we explore connections between this model and Cox processes --- that is Poisson processes with random intensities. We apply the modelling framework to data on trades in IBM shares.

van der Waals interaction of parallel polymers and nanotubes

We study the mutual interactions of simple, parallel polymers and nanotubes, and develop a scheme to include the van der Waals interactions in the framework of density functional theory (DFT) for these molecules at intermediate to long-range separations. We primarily focus on the polymers polyethylene, isotactic polypropylene, and isotactic polyvinylchloride, but our approach applies more generally to all simple polymers and nanotubes. From first-principle DFT calculations we extract the electron density of the polymers and their static electric response. We derive explicit expressions for the van der Waals interaction energy under simple symmetry assumptions.Comment: 8 pages, 2 figures (2 eps figure files

Dynamics of trade-by-trade price movements: decomposition and models

In this paper we introduce a decomposition of the joint distribution of price changes of assets recorded trade--by--trade. Our decomposition means that we can model the dynamics of price changes using quite simple and interpretable models which are easily extended in a great number of directions, including using durations and volume as explanatory variables. Thus we provide an econometric basis for empirical work on market microstructure using time series of transactions data. We use maximum likelihood estimation and testing methods to assess the fit of the model to a year of IBM stock price data taken from the New York Stock Exchange.Activity, autologistic, conditional independence, decomposition, directions, durations, forecasting, GLARMA, logarithmic distribution, prediction decomposition, size, transactions data.

A summary report on system effectiveness and optimization study

Report treats optimization and effectiveness separately. Report illustrates example of dynamic programming solution to system optimization. Computer algorithm has been developed to solve effectiveness problem and is included in report

Detection of isolated population III stars with the James Webb Space Telescope

The first population III stars are predicted to form in minihalos at a redshift of approximately 10-30. The James Webb Space Telescope (JWST), tentatively scheduled for launch in 2018, will probably be able to detect some of the first galaxies, but whether it will also be able to detect the first stars remains more doubtful. Here, we explore the prospects of detecting an isolated population III star or a small cluster of population III stars down to redshift 2 in either lensed or unlensed fields. Our calculations are based on realistic stellar atmospheres and take into account the potential flux contribution from the surrounding HII region. We find that unlensed population III stars are beyond the reach of JWST, and that even lensed population III stars will be extremely difficult to detect. However, the main problem with the latter approach is not necessarily that the lensed stars are too faint, but that their surface number densities are too low. To detect even one population III star of 60 solar masses when pointing JWST through the galaxy cluster MACS J0717.5+3745, the lensing cluster with the largest Einstein radius detected so far, the cosmic star formation rate of population III stars would need to be approximately an order of magnitude higher than predicted by the most optimistic current models.Comment: 8 pages, 6 figures, 1 table, published in MNRAS. The main change in version 2 is the inclusion of lower redshifts, down to 2. There was also one more SFR comparison model (Tornatore 2007) adde

Investigating the selectivity of weed harrowing with new methods

In six field experiments it was investigated whether row spacing, timing, direction and orientation of post-emergence weed harrowing in spring barley influenced the selectivity and whether it is important that increasing intensities of harrowing are generated either by increasing number of passes or increasing driving speed. Selectivity was defined as the relationship between crop burial in soil immediately after treatment and weed control. To estimate crop burial, digital image analysis was used in order to make the estimations objective. The study showed that narrow row spacing decreased selectivity in a late growth stage (21) whereas row spacing in the range of 5.3 cm to 24 cm had no effects in an early growth stage (12). Harrowing across rows decreased selectivity in one out of two experiments. Whether repeated passes with the harrowing were carried out in the same orientation along the rows or in alternative orientations forth and back was unimportant. There were indications that high driving speed decreases selectivity and that repeated passes with low driving speed are better than single treatments with high driving speed. Impacts on selectivity, however, were small and only significant at high degrees of weed control. Timing had no significant impact on selectivity