299 research outputs found
Implementing Affordable Socially Assistive Pet Robots in Care Homes Before and During the COVID-19 Pandemic: Stratified Cluster Randomized Controlled Trial and Mixed Methods Study.
BACKGROUND: Robot pets may assist in the challenges of supporting an aging population with growing dementia prevalence. Prior work has focused on the impacts of the robot seal Paro on older adult well-being, but recent studies have suggested the good acceptability and implementation feasibility of more affordable devices (Joy for All [JfA] cats and dogs). OBJECTIVE: We aimed to address the limited effectiveness research on JfA devices. METHODS: We conducted an 8-month, stratified, cluster randomized controlled trial in 8 care homes in Cornwall, United Kingdom. Over 4 months, 4 care homes each received 2 JfA devices (1 cat and 1 dog; intervention group), and 4 homes received care as usual (control group). Psychometrics were collected before and after the intervention to compare the change from baseline to follow-up between the groups. In the final 4 months, all 8 care homes received devices, but only qualitative data were collected owing to COVID-19 and reduced capacity. The primary outcome was neuropsychiatric symptoms (Neuropsychiatric Inventory [NPI] Nursing Home version). Care provider burden was a secondary outcome (occupational disruptiveness NPI subscale), alongside the Challenging Behavior scale, the Holden communication scale, the Campaign to End Loneliness questionnaire, and medication use. Qualitative data were collected through care staff observation calendars and end-of-study interviews to understand use, experience, and impact. We also collected demographic data and assessed dementia severity. In total, 253 residents had robot interaction opportunities, and 83 were consented for direct data collection. RESULTS: There was a significant difference in the total change from baseline to follow-up between the intervention and control groups for NPI (P<.001) and occupational disruptiveness (P=.03). Neuropsychiatric symptoms increased in the control group and decreased in the intervention group. No significant difference was seen for communication issues or challenging behavior. For NPI subdomains, there were significant differences from baseline to follow-up in delusions (P=.03), depression (P=.01), anxiety (P=.001), elation (P=.02), and apathy (P=.009), all of which decreased in the intervention group and increased slightly in the control group. The summative impact results suggested that most residents (46/54, 85%) who interacted with robots experienced a positive impact. Those who interacted had significantly higher dementia severity scores (P=.001). The qualitative results suggested good adoption, acceptability, and suitability for subjectively lonely individuals and lack of a novelty effect through sustained use, and demonstrated that the reasons for use were entertainment, anxiety, and agitation. CONCLUSIONS: Affordable robot pets hold potential for improving the well-being of care home residents and people with dementia, including reducing neuropsychiatric symptoms and occupational disruptiveness. This work suggests no novelty effect and contributes toward understanding robot pet suitability. Moreover, interactions were more common among residents with more moderate/severe dementia and those subjectively lonely. TRIAL REGISTRATION: ClinicalTrials.gov NCT04168463; https://www.clinicaltrials.gov/ct2/show/NCT0416846
Griffiths-McCoy singularities in the transverse field Ising model on the randomly diluted square lattice
The site-diluted transverse field Ising model in two dimensions is studied
with Quantum-Monte-Carlo simulations. Its phase diagram is determined in the
transverse field (Gamma) and temperature (T) plane for various (fixed)
concentrations (p). The nature of the quantum Griffiths phase at zero
temperature is investigated by calculating the distribution of the local
zero-frequency susceptibility. It is pointed out that the nature of the
Griffiths phase is different for small and large Gamma.Comment: 21 LaTeX (JPSJ macros included), 12 eps-figures include
Finite Temperature and Dynamical Properties of the Random Transverse-Field Ising Spin Chain
We study numerically the paramagnetic phase of the spin-1/2 random
transverse-field Ising chain, using a mapping to non-interacting fermions. We
extend our earlier work, Phys. Rev. 53, 8486 (1996), to finite temperatures and
to dynamical properties. Our results are consistent with the idea that there
are ``Griffiths-McCoy'' singularities in the paramagnetic phase described by a
continuously varying exponent , where measures the
deviation from criticality. There are some discrepancies between the values of
obtained from different quantities, but this may be due to
corrections to scaling. The average on-site time dependent correlation function
decays with a power law in the paramagnetic phase, namely
, where is imaginary time. However, the typical
value decays with a stretched exponential behavior, ,
where may be related to . We also obtain results for the full
probability distribution of time dependent correlation functions at different
points in the paramagnetic phase.Comment: 10 pages, 14 postscript files included. The discussion of the typical
time dependent correlation function has been greatly expanded. Other papers
of APY are available on-line at http://schubert.ucsc.edu/pete
Critical Behavior and Griffiths-McCoy Singularities in the Two-Dimensional Random Quantum Ising Ferromagnet
We study the quantum phase transition in the two-dimensional random Ising
model in a transverse field by Monte Carlo simulations. We find results similar
to those known analytically in one-dimension. At the critical point, the
dynamical exponent is infinite and the typical correlation function decays with
a stretched exponential dependence on distance. Away from the critical point
there are Griffiths-McCoy singularities, characterized by a single,
continuously varying exponent, z', which diverges at the critical point, as in
one-dimension. Consequently, the zero temperature susceptibility diverges for a
RANGE of parameters about the transition.Comment: 4 pages RevTeX, 3 eps-figures include
Quantum Spin Glasses
Ising spin glasses in a transverse field exhibit a zero temperature quantum
phase transition, which is driven by quantum rather than thermal fluctuations.
They constitute a universality class that is significantly different from the
classical, thermal phase transitions. Most interestingly close to the
transition in finite dimensions a quantum Griffiths phase leads to drastic
consequences for various physical quantities: for instance diverging magnetic
susceptibilities are observable over a whole range of transverse field values
in the disordered phase.Comment: 10 pages LaTeX (Springer Lecture Notes style file included), 1
eps-figure; Review article for XIV Sitges Conference: Complex Behavior of
Glassy System
Numerical Study of Spin and Chiral Order in a Two-Dimensional XY Spin Glass
The two dimensional XY spin glass is studied numerically by a finite size
scaling method at T=0 in the vortex representation which allows us to compute
the exact (in principle) spin and chiral domain wall energies. We confirm
earlier predictions that there is no glass phase at any finite T. Our results
strongly support the conjecture that both spin and chiral order have the same
correlation length exponent . We obtain preliminary results
in 3d.Comment: 4 pages, 2 figures, revte
Random quantum magnets with long-range correlated disorder: Enhancement of critical and Griffiths-McCoy singularities
We study the effect of spatial correlations in the quenched disorder on
random quantum magnets at and near a quantum critical point. In the random
transverse field Ising systems disorder correlations that decay algebraically
with an exponent rho change the universality class of the transition for small
enough rho and the off-critical Griffiths-McCoy singularities are enhanced. We
present exact results for 1d utilizing a mapping to fractional Brownian motion
and generalize the predictions for the critical exponents and the generalized
dynamical exponent in the Griffiths phase to d>=2.Comment: 4 pages RevTeX, 1 eps-figure include
Griffiths-McCoy Singularities in the Random Transverse-Field Ising Spin Chain
We consider the paramagnetic phase of the random transverse-field Ising spin
chain and study the dynamical properties by numerical methods and scaling
considerations. We extend our previous work [Phys. Rev. B 57, 11404 (1998)] to
new quantities, such as the non-linear susceptibility, higher excitations and
the energy-density autocorrelation function. We show that in the Griffiths
phase all the above quantities exhibit power-law singularities and the
corresponding critical exponents, which vary with the distance from the
critical point, can be related to the dynamical exponent z, the latter being
the positive root of [(J/h)^{1/z}]_av=1. Particularly, whereas the average spin
autocorrelation function in imaginary time decays as [G]_av(t)~t^{-1/z}, the
average energy-density autocorrelations decay with another exponent as
[G^e]_av(t)~t^{-2-1/z}.Comment: 8 pages RevTeX, 8 eps-figures include
Dynamic Scaling in Diluted Systems Phase Transitions: Deactivation trough Thermal Dilution
Activated scaling is confirmed to hold in transverse field induced phase
transitions of randomly diluted Ising systems. Quantum Monte Carlo calculations
have been made not just at the percolation threshold but well bellow and above
it including the Griffiths-McCoy phase. A novel deactivation phenomena in the
Griffiths-McCoy phase is observed using a thermal (in contrast to random)
dilution of the system.Comment: 4 pages, 4 figures, RevTe
Numerical Study of Order in a Gauge Glass Model
The XY model with quenched random phase shifts is studied by a T=0 finite
size defect energy scaling method in 2d and 3d. The defect energy is defined by
a change in the boundary conditions from those compatible with the true ground
state configuration for a given realization of disorder. A numerical technique,
which is exact in principle, is used to evaluate this energy and to estimate
the stiffness exponent . This method gives in
2d and in 3d, which are considerably larger than
previous estimates, strongly suggesting that the lower critical dimension is
less than three. Some arguments in favor of these new estimates are given.Comment: 4 pages, 2 figures, revtex. Submitted to Phys. Rev. Let
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