Interdevice reliability and validity assessment of the Nicholas Hand-Held Dynamometer.

The Nicholas Hand-Held Dynamometer (HHD) has been shown to have excellent interday and intraday reliability when using the same HHD. Since clinics may have more than one HHD with which to evaluate patients, it would be of value to know if two identical HHDs measure the same variable consistently. The purpose of this investigation was to assess interdevice reliability of the Nicholas HHD as well as to determine its validity. Thirty healthy female subjects between the ages of 20 and 56 years (mean age = 28.4) were tested for hamstring strength. Three measurements of maximum hamstring contractions were obtained using the first HHD (Device A). The average of these three measurements was compared with the average of three measurements obtained after a brief rest using a second HHD (Device B). Measurements from the two HHDs were also compared with measurements obtained from a Kin-Com isokinetic dynamometer. The Kin-Com measurements were used as criteria to determine validity of the HHD. An intraclass correlation coefficient (ICC) calculated to determine reliability between the two HHDs was low (ICC = .58). Pearson product-moment correlation coefficients were calculated between the Kin-Com and each of the two HHDs. These values were .85 and .83 for Device A and B, respectively. Analysis of variance showed no significant difference between the Kin-Com and Device A but a significant difference between the Kin-Com and Device B (p < .001). Measurements obtained from two identical HHDs may be significantly different and should not be compared.

The influence of personal and collective self-esteem on strategies of social differentiation.

The present study distinguished between personal self-esteem (PSE) and collective self-esteem (CSE) as determinants of in-group bias in an intergroup context. Subjects performed a group task, the product of which they subsequently evaluated ('own' group), along with solutions allegedly produced by another 'in-group' (similar nationality), and an 'out-group' (different nationality). This provided the opportunity for intragroup discrimination (own vs. in-group), and both direct (own vs. out-group) and indirect (in-group vs. out-group) strategies of intergroup discrimination. It was predicted that subjects high in CSE would differentiate more than subjects low in CSE, both directly and indirectly, but that intergroup discrimination would also result from high PSE. The relationship between the in-group and out-group was also manipulated by varying the salient out-group. It was predicted that subjects motivated to enhance social identity (high CSE) would differentiate more, directly and indirectly, when the out-group was seen as having a more competitive relationship with the in-group. Although this manipulation was unsuccessful, a follow-up suggested that the out-group predefined as less competitive was actually a more relevant comparison group in the context of the task, which is consistent with effects of this manipulation. Overall PSE and CSE were both found to influence differentiation at the intragroup and intergroup level, both independently and interactively. However, whereas high PSE led to greater positive differentiation, low CSE had this effect, and a combination of high PSE and low CSE produced the most consistent pattern of positive in-group differentiation across both out-group conditions. Possible mechanisms which account for this pattern are discussed and the relationship between dimensions of self-esteem and group differentiation is reappraised in the light of these findings.

The involvement of photosystem II-generated H2O2 in photoinhibition.

The involvement of H2O2 generated by photosystem II (PSII) in the process of photoinhibition of thylakoids with a functional oxygen-evolving complex (OEC) was investigated. The rate of photoinhibition was decreased to the rate of loss of activity in the dark when bovine Fe-catalase was present during the photoinhibitory illumination. Photoinhibition was accelerated for both Cl(-)-depleted and Cl(-)-sufficient thylakoids when KCN was present to inhibit the thylakoid-bound Fe-catalase. We propose that these preparations become photoinhibited by reactions with H2O2 produced via oxidation of water by the Cl(-)-depleted OEC and by reduction of O2 at the QB site when PSII is illuminated without an electron acceptor.