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.
Neutrons produced by the carbon fusion reaction 12C(12C,n)23Mg play an important role in stellar nucleosynthesis. However, past studies have shown large discrepancies between experimental data and ...theory, leading to an uncertain cross section extrapolation at astrophysical energies. We present the first direct measurement that extends deep into the astrophysical energy range along with a new and improved extrapolation technique based on experimental data from the mirror reaction 12C(12C,p)23Na. The new reaction rate has been determined with a well-defined uncertainty that exceeds the precision required by astrophysics models. Using our constrained rate, we find that 12C(12C,n)23Mg is crucial to the production of Na and Al in Pop-III Pair Instability Supernovae. It also plays a non-negligible role in the production of weak s-process elements as well as in the production of the important galactic gamma-ray emitter 60Fe.
It is well established that low cerebrospinal fluid (CSF) pH and high CSF lactate concentration indicate the development of brain acidosis after severe human head injury. However, there is no direct ...evidence that tissue acidosis actually occurs. We measured brain extracellular pH (pHe) in three patients undergoing operation for the evacuation of acute subdural hematomas. A pH-sensitive polymer membrane electrode was inserted 500 micron into the cerebral cortex close to the damaged area. The pHe values obtained were correlated with ventricular CSF acid-based parameters and extension of the brain lesion. The CSF pH was higher than the pHe in all cases; the pHe was particularly low in areas of contusion or compression by mass lesion. The effect of focal brain tissue acidosis on clinical course after severe head injury is discussed.
As the demand for ever shallower, highly active and abrupt junctions continues, it is important to look at both the doping and activation portions of junction formation as a unit process. Advanced ...doping is useless without annealing methods that limit diffusion and provide high levels of electrical activation and new annealing techniques cannot make the junctions shallower than the as-doped profiles. This work has looked at optimizing several types of advanced doping (Plasma Doping and beamline ion implantation of molecular dopants) and a flash lamp-based ms annealing approach. With this combination, very shallow, abrupt and low resistivity junctions can be formed. Careful characterization was used to ensure the accuracy of the sheet resistance and junction depth measurements.
