Magnetization of La(2-x)Sr(x)NiO(4+ delta) (0 < x < 0.5) and observation of novel memory effects

We have studied the magnetization of a series of spin-charge ordered La(2-x)Sr(x)NiO(4+delta) single crystals with 0 < x < 0.5. For fields applied parallel to the ab plane there is a large irreversibility below a temperature T(F1) ~ 50 K and a smaller irreversibility that persists up to near the charge ordering temperature. We observed a novel memory effect in the thermo-remnant magnetization across the entire doping range. We found that these materials retain a memory of the temperature at which an external field was removed, and that there is a pronounced increase in the thermo-remnant magnetization when the system is warmed through a spin reorientation transition.Comment: 11 pages, 12 figure

The effects of perceived and received support on self-confidence.

types: Journal ArticleCopyright © 2007 Taylor & Francis. This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Sports Sciences, available online: http://www.tandfonline.com/doi/abs/10.1080/02640410600982279A sample of 222 university athletes (mean age 19.8 years, s = 2.0), ranging in standard from university second team to international competitor, completed a measure of perceived support 2 weeks before an important competition or match. On the day before the competition or match, the athletes completed measures of stressors, stress, received support, and self-confidence. Moderated hierarchical regression analyses revealed the following key findings: (i) main effects for both perceived (DeltaR2 = 0.11) and received support (DeltaR2 = 0.14) upon self-confidence; (ii) stress-buffering effects for both perceived (DeltaR2 = 0.02) and received (DeltaR2 = 0.07) support upon self-confidence; (iii) when both aspects of support were considered simultaneously, stress-buffering effects were primarily attributable to the influence of received support. These results demonstrate the beneficial impact of social support on self-confidence, both directly and by reducing the negative effect of stress on self-confidence. Our findings emphasize the need to recognize the distinction between perceived and received support, both in terms of theory and the design of social support interventions with athletes

Social Support and Performance in a Golf-Putting Experiment

publication-status: Publishedtypes: Articleas accepted for publication© 2010 Human Kinetics, Inc.This study examined the impact of a social support manipulation on performance. Participants with high and low levels of perceived support were randomly assigned to an experimental support or control condition, before completing a golf-putting task. Participants with high levels of perceived support performed at a higher level than those with low levels of perceived support. Participants in the support condition performed at a higher level than those in the control condition. A significant interaction was primarily attributable to the low perceived support participants in the support condition performing better than the low perceived support participants in the control condition. Participants in the support condition also experienced less frequent and distracting task-irrelevant thoughts compared with those in the control condition. These results suggest that experimentally manipulated support may lead to improvements in the performance of novices completing a golf-putting task, and that such support may be particularly important for those low in perceived support

The PASS-Q: the perceived available support in sport questionnaire.

This article provides initial evidence for the construct validity of the Perceived Available Support in Sport Questionnaire (PASS-Q), which assesses emotional, esteem, informational, and tangible support. In Study 1, confirmatory factor analyses provided evidence for a four-dimension factor structure. Correlations supported hypothesized relationships between the PASS-Q dimensions and the Social Support Survey questions (Richman, Rosenfeld, & Hardy, 1993). In Study 2, the four-dimension factor structure was supported in an independent sample. Further, higher levels of perceived available emotional, esteem, informational, and tangible support were associated with higher levels of self-confidence and lower levels of burnout. Researchers are encouraged to use the PASS-Q to examine the effects of perceived available support in sport contexts

Spin reorientation transition in the incommensurate stripe-ordered phase of La3/2Sr1/2NiO4

The spin ordering of La3/2Sr1/2NiO4 was investigated by magnetization measurements, and by unpolarized- and polarized-neutron diffraction. Spin ordering with an incommensurability epsilon ~ 0.445 is observed below T_so ~ 80 K. On cooling, a spin reorientation is observed at 57 +/- 1 K, with the spin axes rotating from 52 +/- 4 degrees to 78 +/- 3 degrees. This is the first time a spin reorientation has been observed in a La2-xSrxNiO4+delta compound having incommensurate stripe order.Comment: REVTex 4. 4 pages including 4 figures. Minor changes to text. Accepted to be published in Physical Review

The Temperature Evolution of the Out-of-Plane Correlation Lengths of Charge-Stripe Ordered La(1.725)Sr(0.275)NiO(4)

The temperature dependence of the magnetic order of stripe-ordered La(1.725)Sr(0.275)NiO(4) is investigated by neutron diffraction. Upon cooling, the widths if the magnetic Bragg peaks are observed to broaden. The degree of broadening is found to be very different for l = odd-integer and l = even-integer magnetic peaks. We argue that the observed behaviour is a result of competition between magnetic and charge order.Comment: 3 figure

A 2D systems approach to iterative learning control for discrete linear processes with zero Markov parameters

In this paper a new approach to iterative learning control for the practically relevant case of deterministic discrete linear plants with uniform rank greater than unity is developed. The analysis is undertaken in a 2D systems setting that, by using a strong form of stability for linear repetitive processes, allows simultaneous con-sideration of both trial-to-trial error convergence and along the trial performance, resulting in design algorithms that can be computed using Linear Matrix Inequalities (LMIs). Finally, the control laws are experimentally verified on a gantry robot that replicates a pick and place operation commonly found in a number of applications to which iterative learning control is applicable

An Intervention to Increase Social Support and Improve Performance

This is a postprint of an article published in Journal of Applied Sport Psychology, 2009, Vol. 21, Issue 2, pp. 186 - 200© 2009 copyright Taylor & Francis. Journal of Applied Sport Psychology is available online at: http://www.tandfonline.com/toc/uasp20/currentThis study investigated the effects of a one-to-one intervention designed to increase social support and improve performance using a single-subject multiple baseline design. Participants were 3 high-level male golfers, mean age 25.0 years (SD = 2.6). All participants reported significantly higher levels of emotional, esteem, informational, and tangible support in the intervention phase compared to the baseline phase (ts = -2.35 to -21.80, ps < .01). The performance of all participants improved during the intervention phase compared to the baseline phase. Participant A improved by an average of .90 shots per round, Participant B by 1.33 shots per round, and Participant C by 3.10 shots per round. The effectiveness of the intervention upon performance outcome was supported by a χ2 analysis (χ2 (1) = 4.80, p < .05). The results indicate that a one-to-one intervention may be a useful strategy to increase social support and improve performance

Enacted support and golf-putting performance: The role of support type and support visibility

Objectives This study examined whether the impact of enacted support on performance differed across type (esteem and informational) and visibility (visible and invisible) of support. It further tested whether self-efficacy mediated the enacted support-performance relationship. Design A one-factor (support manipulation) between subjects experiment. Method A fellow novice golfer — in reality a confederate — was scripted to randomly provide one of five support manipulations (visible informational support, invisible informational support, visible esteem support, invisible esteem support, and no support) to participants (n = 105). Immediately after, participants completed a self-efficacy measure and then performed a golf-putting task. Results The results demonstrated that participants given visible esteem support significantly outperformed those given no support and those given invisible esteem support. Participants given invisible informational support significantly outperformed those given no support. Although non-significant, the observed mean difference and moderate effect size provided weak evidence that those in the invisible informational support condition may have performed at a higher level than those in the visible informational support condition. There was no evidence that self-efficacy could explain any of these effects. Conclusion The results suggest that enacted support can benefit novices’ performance and that it is crucial to consider both the type and the visibility of the support. Esteem support is particularly effective when communicated in an explicit and direct manner but informational support appears more effective when communicated in a more subtle, indirect manner

Stressors, social support, and effects upon performance in golf.

types: Journal ArticleCopyright © 2000 Taylor & Francis. This is an Author's Accepted Manuscript of an article published in Journal of Sports Sciences available online at: http://www.tandfonline.com/doi/abs/10.1080/02640410600702974#.VN3bWp1FDcsIn this study, we extended the work of Rees and Hardy (2004) by examining the main and stress-buffering effects of social support upon sports performance in a different context, using a different outcome measure, and a specific time-frame. A high-level performance sample of 117 male golfers (mean age 24.8, s = 8.3) completed measures of social support and stressors before competitions. Performance outcome was recorded. Moderated hierarchical regression analyses revealed significant (P < 0.05) main effects for stressors upon performance in 8 of the 11 models tested (R2 = 0.08 - 0.21). Over and above the variance accounted for by stressors, there were significant (P < 0.05) main effects for social support upon performance in all models tested (DeltaR2 = 0.10 - 0.24). In all models, stressors were associated with worse performance, whereas social support was associated with better performance. There were no significant interactions (stress-buffering effects). Main effects for social support upon performance suggest that social support may have aided performance directly, regardless of the level of stress