The mediating effects of leisure engagement on relationships between caregiving stress and subjective wellbeing among family caregivers of persons with cognitive impairment: A cross-sectional study.

Family caregivers of persons with cognitive impairment experience changes in reductions in leisure engagement, which can decrease their subjective wellbeing (leisure satisfaction, negative affect and positive affect). We recruited 100 dyads of patients with cognitive impairment and family caregivers by convenience sampling from outpatient memory clinics and daycare centers in northern Taiwan. Hierarchical regression analysis tested the mediating effects of leisure engagement on the relationship between caregiving stress and subjective wellbeing. Results indicated that the restorative experience of event/tourism activities (ß = 0.23, p < .05) significantly mediated between caregiving stress and leisure satisfaction. In addition, the only significant mediator between caregiving stress and negative affect was leisure barriers (ß = 0.21, p < .05). Both of the regression models explained 27% of the variance. Future development of leisure interventions should focus on reducing leisure barriers and providing event and tourism activities to the dyads. (146 words).

Numerical renormalization-group approach to a sandpile.

Multiple topplings and grain redistribution are two essential features in sandpile dynamics. A renormalization group (RG) approach incorporating these features is investigated. The full enumeration of all relaxations involving such an approach is difficult. Instead, we developed an efficient procedure to sample the relaxations. We applied this RG scheme to a square lattice and a triangular lattice. As shown by the fixed point analysis on a square lattice, the effect of multiple topplings leads the resultant height probabilities towards the exact solution while the effect of grain redistribution does not.

Effects of bulk dissipation on the critical exponents of a sandpile.

Bulk dissipation of a sandpile on a square lattice with the periodic boundary condition is investigated through a dissipating probability f during each toppling process. We find that the power-law behavior is broken for f>10(-1) and not evident for 10(-1)}>f>10(-2). In the range 10(-2)>or=f>or=10(-5), numerical simulations for the toppling size exponents of all, dissipative, and last waves have been studied. Two kinds of definitions for exponents are considered: the exponents obtained from the direct fitting of data and the exponents defined by the simple scaling. Our result shows that the exponents from these two definitions may be different. Furthermore, we propose analytic expressions of the exponents for the direct fitting, and it is consistent with the numerical result. Finally, we point out that small dissipation drives the behavior of this model toward the simple scaling.

Parallel tempering simulations of HP-36.

We report results from all-atom Monte Carlo simulations of the 36-residue villin headpiece subdomain HP-36. Protein-solvent interactions are approximated by an implicit solvent model. The parallel tempering is used to overcome the problem of slow convergence in low-temperature protein simulations. Our results show that this technique allows one to sample native-like structures of small proteins and points out the need for improved energy functions.

Renormalization-group approach to an Abelian sandpile model on planar lattices.

One important step in the renormalization-group (RG) approach to a lattice sandpile model is the exact enumeration of all possible toppling processes of sandpile dynamics inside a cell for RG transformations. Here we propose a computer algorithm to carry out such exact enumeration for cells of planar lattices in the RG approach to the Bak-Tang-Wiesenfeld sandpile model [Phys. Rev. Lett. 59, 381 (1987)] and consider both the reduced-high RG equations proposed by Pietronero, Vespignani, and Zapperi (PVZ) [Phys. Rev. Lett. 72, 1690 (1994)], and the real-height RG equations proposed by Ivashkevich [Phys. Rev. Lett. 76, 3368 (1996)]. Using this algorithm, we are able to carry out RG transformations more quickly with large cell size, e.g., 3x3 cell for the square (SQ) lattice in PVZ RG equations, which is the largest cell size at the present, and find some mistakes in a previous paper [Phys. Rev. E 51, 1711 (1995)]. For SQ and plane triangular (PT) lattices, we obtain the only attractive fixed point for each lattice and calculate the avalanche exponent tau and the dynamical exponent z. Our results suggest that the increase of the cell size in the PVZ RG transformation does not lead to more accurate results. The implication of such result is discussed.

Renormalization-group approach to the Manna sandpile.

In this paper a renormalization group (RG) scheme for the q -state Manna model is proposed based on the stochastic characteristic and the similarity of topplings at different scales. A full enumeration of the RG evolution events inside a 2 x 2 RG cell for q=2 , 3, and 4 was carried out. A fixed point analysis shows that the resulting height probabilities are very close to the results obtained by the numerical simulations. The calculations of the toppling number exponent tau and the dynamical exponent z are also provided. It was found that the RG values of tau and z for q=4 are very close to the simulation values.