The low-lying energy levels of proton-rich \(^{56}\)Cu have been extracted using in-beam \(\gamma\)-ray spectroscopy with the state-of-the-art \(\gamma\)-ray tracking array GRETINA in conjunction ...with the S800 spectrograph at the National Superconducting Cyclotron Laboratory at Michigan State University. Excited states in \(^{56}\)Cu serve as resonances in the \(^{55}\)Ni(p,\(\gamma\))\(^{56}\)Cu reaction, which is a part of the rp-process in type I x-ray bursts. To resolve existing ambiguities in the reaction Q-value, a more localized IMME mass fit is used resulting in \(Q=639\pm82\)~keV. We derive the first experimentally-constrained thermonuclear reaction rate for \(^{55}\)Ni(p,\(\gamma\))\(^{56}\)Cu. We find that, with this new rate, the rp-process may bypass the \(^{56}\)Ni waiting point via the \(^{55}\)Ni(p,\(\gamma\)) reaction for typical x-ray burst conditions with a branching of up to \(\sim\)40\(\%\). We also identify additional nuclear physics uncertainties that need to be addressed before drawing final conclusions about the rp-process reaction flow in the \(^{56}\)Ni region.
The development of a scale to measure youth athletes' perception of risk of injury in sports using a multi-phase approach is discussed. In Phase One, using the methodology outlined by Vaugh et al. ...(1996), focus groups were conducted with 21 youth athletes to generate potential items for the scale. The items were then categorized into five theme areas: (a) collision injuries, (b) injuries in practice or games, (c) overuse injuries, (d) specific injury types, and (e) surface and equipment injuries. A total of 36 items were generated to form the initial pilot scale. For Phase Two, the pilot scale was completed by 136 youth athletes aged 11 to 14. Using Cronbach's alpha, reliability for the scale was .94. All items positively contributed to the alpha total. Intercorrelations between individual items ranged from .01 to .64 indicating low to moderate correlations, but no multicollinearity problems. The results of an exploratory factor analysis suggested that the scale was unidimensional. The initial unidimensionality of the scale is explored in light of the athletic-specific perception of risk of injury as a subcomponent of a general perception of risk of injury. The implication of this finding in relation to internal consistency is also addressed. Phase Three involved the administration of the scale to a larger sample (N = 450) to confirm the unidimensional or five factor structure of the scale. The results of the confirmatory factor analysis as well as the initial relationship between the scale and previous injuries are presented. The examination of the predictive validity of the scale using a path model, and the development of testing norms are also discussed.
BACKGROUND AND PURPOSE: We investigated the role of actin polymerization in regulating arterial diameter in response to increasing pressure and modulating forced dilatation of cerebral arteries at ...pressures above the upper limit of autoregulation. METHODS: Posterior cerebral arteries (n = 12) were isolated and pressurized in a special arteriograph that allowed control of intravascular pressure and measurement of lumen diameter. Intact arteries in the absence (control) or presence of 3.0 mumol/L cytochalasin B (CB), an inhibitor of actin polymerization, were subjected to stepwise increases in pressure from 75 to 200 mm Hg. Lumen diameter was continuously recorded, as was the pressure at which forced dilatation (loss of tone) occurred. After a period of time at 200 mm Hg, pressure was returned to 75 mm Hg and the extent of tone recovery was evaluated. RESULTS: Arteries with and without CB developed a similar amount of tone during equilibration at 75 mm Hg: percent tone = 27 +/- 3% for control versus 29 +/- 4% for CB arteries (P 0.05). However, arteries in the presence of CB could not withstand pressure as well and underwent FD at significantly lower pressures: 168 +/- 5 mm Hg for control versus 142 +/- 5 mm Hg for CB arteries (P 0.01). The amount of tone that arteries regained after FD when pressure was returned to 75 mm Hg was also less in CB arteries: percent tone = 34 +/- 3% for control versus 11 +/- 2% for CB arteries (P 0.01). CONCLUSIONS: Cytoskeletal integrity appears important for maintaining cerebral arterial diameter during changing intravascular pressure. In addition, the process of actin polymerization may be a significant contributor to development of myogenic tone after forced dilatation.
