34 resultados para Neutron moderation
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This study examined the relations of organizational commitment and demographic factors with objectively measured absence frequency data of 106 staff at a UK school, collected over a 1-year period. We found significant associations of commitment and absenteeism, with high affective and normative commitment, and low continuance commitment being associated with lower levels of absence. Age moderated two of these associations, with low normative commitment and high continuance commitment predicting absence most strongly for older workers. Our findings help practitioners and researchers to understand how commitment may interact with other factors to predict absence. Interaction effects in our data showed that absence frequencies tended to be highest for older workers who felt a lower sense of obligation to their organization, or a lack of alternatives to their present employment. © 2012 Hogrefe Publishing.
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Addressing inconsistencies in relational demography research, we examine the relationship between cultural dissimilarity and individual performance through the lens of social self-regulation theory, which extends the social identity perspective in relational demography with the analysis of social self-regulation. We propose that social self-regulation in culturally diverse teams manifests itself as performance monitoring (i.e., individuals' actions to meet team performance standards and peer expectations). Contingent on the status associated with individuals' cultural background, performance monitoring is proposed to have a curvilinear relationship with individual performance and to mediate between cultural dissimilarity and performance. Multilevel moderated mediation analyses of time-lagged data from 316 members of 69 teams confirmed these hypotheses. Cultural dissimilarity had a negative relationship with performance monitoring for high cultural-status members, and a positive relationship for low cultural-status members. Performance monitoring had a curvilinear relationship with individual performance that became decreasingly positive. Cultural dissimilarity thus was increasingly negatively associated with performance for high culturalstatus members, and decreasingly positively for low cultural-status members. These findings suggest that cultural dissimilarity to the team is not unconditionally negative for the individual but, in moderation, may in fact have positive motivational effects.
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We use the self-concept based theory of leadership and social exchange theory to hypothesize processes linking transformational leadership to follower performance outcomes. Specifically, we hypothesize that (a) transformational leadership relates to followers' work engagement both directly and indirectly through their psychological states, (b) work engagement relates to innovative behavior, (c) innovative behavior relates to task performance, and (d) the work engagement–innovative behavior relationship is moderated by leader–member exchange. Results from a test of these relationships in a sample of employees of a large telecommunication company in China largely support our hypothesized model.
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The role of the Sm3+ ions in the structure of vitreous Sm2O3•4P2O5 has been investigated using the neutron diffraction anomalous dispersion technique, which employs the wavelength dependence of the real and imaginary parts of the neutron scattering length close to an absorption resonance. The data described here represent the first successful complete neutron anomalous dispersion study on an amorphous material. This experimental methodology permits one to determine exclusively the closest Sm• •• Sm separation. Knowledge of the R•••R (R = rare-earth) pairwise correlation is key to understanding the optical and magnetic properties of rare-earth phosphate glasses. The anomalous difference correlation function, ΔT''(r), shows a dominant feature pertaining to a Sm•••Sm separation, centred at 4.8 Å. The substantial width and marked asymmetry of this peak indicates that the minimum approach of Sm3+ ions could be as close as 4 Å. Information on other pairwise correlations is also revealed via analysis of T (r) and ΔT (r) correlation functions: Sm3+ ions display an average co-ordination number, n Sm(O), of 7, with a mean Sm–O bond length of 2.375(5) Å whilst the PO4 tetrahedra have a mean P–O bond length of 1.538(2) Å. Second- and third-neighbour correlations are also identified. These results corroborate previous findings. Such consistency lends support to the application of the anomalous dispersion technique to determine separations.
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A magnetic difference neutron diffraction study of a rare-earth (Tb) phosphate glass has revealed exclusively the Tb...Tb distances. The difference between data taken with and without an applied magnetic field of 4 T shows Tb...Tb pairwise atomic correlations at 3.9 and 6.4 A, respectively, with relative coordination numbers of 1:14. The first distance arises when two Tb3+ ions share a common oxygen neighbor, and indicates a clustering of rare-earth ions. The second distance arises when two Tb3+ ions are coordinated to different oxygens in the same PO4 group, in a near-linear arrangement.
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Meta-analysis was used to quantify the moderating effects of seven properties of cognitions-accessibility, temporal stability, direct experience, involvement, certainty, ambivalence and affective-cognitive consistency-on cognition-intention and cognition-behaviour relations. Literature searches revealed 44 studies that could be included in the review. Findings showed that all of the properties, except involvement, moderated attitude-behaviour consistency. Similarly, all relevant moderators improved the consistency between intentions and behaviour. Temporal stability moderated PBC-behaviour relations, certainty moderated subjective norm-intention relations, and ambivalence, certainty, and involvement all moderated attitude-intention relations. Overall, temporal stability appeared to be the strongest moderator of cognition-behaviour relations.
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Neutron diffraction was used to measure the structure of the phosphate glasses RAl0.30P3.05O9.62, where R denotes Dy or Ho, and RAl0.34P3.20O10.04, where R denotes La or Ce. For each glass, isomorphic structures were assumed and difference function methods were employed to separate, essentially, those correlations involving the rare-earth ion, R3+, from the remainder. The ratio of bridging oxygen, OB, to terminal oxygen, OT, atoms in the PO4 tetrahedra was quantified and in both materials R3+ and Al3+ are found to act as network modifying cations which bind to the OT. The R–OT coordination number is 6.7(1) and 7.5(2) for the Dy/Ho and La/Ce glasses respectively.
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The relative distribution of rare-earth ions R3+ (Dy3+ or Ho3+) in the phosphate glass RAl0.30P3.05O9.62 was measured by employing the method of isomorphic substitution in neutron diffraction and, by taking the role of Al into explicit account, a self-consistent model of the glass structure was developed. The glass network is found to be made from corner sharing PO4 tetrahedra in which there are, on average, 2.32(9) terminal oxygen atoms, OT, at 1.50(1) Å and 1.68(9) bridging oxygen atoms, OB, at 1.60(1) Å. The network modifying R3+ ions bind to an average of 6.7(1) OT and are distributed such that 7.9(7) R–R nearest neighbours reside at 5.62(6) Å. The Al3+ ion also has a network modifying role in which it helps to strengthen the glass through the formation of OT–Al–OT linkages. The connectivity of the R-centred coordination polyhedra in (M2O3)x(P2O5)1−x glasses, where M3+ denotes a network modifying cation (R3+ or Al3+), is quantified in terms of a parameter fs. Methods for reducing the clustering of rare-earth ions in these materials are then discussed, based on a reduction of fs via the replacement of R3+ by Al3+ at fixed total modifier content or via a change of x to increase the number of OT available per network modifying M3+ cation.
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Neutron diffraction was used to measure the total structure factors for several rare-earth ion R3+ (La3+ or Ce3+) phosphate glasses with composition close to RAl0.35P3.24O10.12. By assuming isomorphic structures, difference function methods were employed to separate, essentially, those correlations involving R3+ from the remainder. A self-consistent model of the glass structure was thereby developed in which the Al correlations were taken into explicit account. The glass network was found to be made from interlinked PO4 tetrahedra having 2.2(1) terminal oxygen atoms, OT, at 1.51(1) Angstrom, and 1.8(1) bridging oxygen atoms, OB, at 1.60(1) Angstrom. Rare-earth cations bonded to an average of 7.5(2) OT nearest neighbors in a broad and asymmetric distribution. The Al3+ ion acted as a network modifier and formed OT-A1-OT linkages that helped strengthen the glass. The connectivity of the R-centered coordination polyhedra was quantified in terms of a parameter f(s) and used to develop a model for the dependence on composition of the A1-OT coordination number in R-A1-P-O glasses. By using recent 17 A1 nuclear-magnetic-resonance data, it was shown that this connectivity decreases monotonically with increasing Al content. The chemical durability of the glasses appeared to be at a maximum when the connectivity of the R-centered coordination polyhedra was at a minimum. The relation of f(s) to the glass transition temperature, Tg, was discussed.