2,421 research outputs found
Local density approximation for confined bosons in an optical lattice
We investigate local and global properties of the one-dimensional
Bose-Hubbard model with an external confining potential, describing an atomic
condensate in an optical lattice. Using quantum Monte Carlo techniques we
demonstrate that a local-density approximation, which relates the unconfined
and the confined model, yields quantitatively correct results in most of the
interesting parameter range. We also examine claims of universal behavior in
the confined system, and demonstrate the origin of a previously calculated fine
structure in the experimentally accessible momentum distribution.Comment: 7 pages, 11 figures; Section III updated and references adde
Phase Diagram of the 1D Kondo Lattice Model
We determine the boundary of the fully polarized ferromagnetic ground state
in the one dimensional Kondo lattice model at partial conduction electron band
filling by using a newly developed infinite size DMRG method which conserves
the total spin quantum number. The obtained paramagnetic to ferromagnetic phase
boundary is below for the whole range of band filling. By this
we solve the controversy in the phase diagram over the extent of the
ferromagnetic region close to half filling.Comment: 6 pages, 4 EPS figures. Presented at MOS9
The Costs of Biosecurity at the Farm Level: the Case of Finnish Broiler
In the European Union, the animal health and food safety strategy includes managing biosecurity along the entire production chain. Farm-level biosecurity provides the foundation for this. However, the farm-level costs of preventive biosecurity have rarely been assessed. Yet many risk management practices are in place constantly regardless of whether there is a disease outbreak or not. We contribute towards filling this information gap by studying the costs incurred in preventive biosecurity by the Finnish poultry farms. In a preliminary analysis, we find that the cost of biosecurity is some 3.55 cents per bird for broiler producers and 75.7 cents per bird for hatching egg producers. The results indicate that work-time devoted to biosecurity represents some 8% of total work time on broiler farms and about 5% on breeder farms.Biosecurity, on-farm costs, poultry, Livestock Production/Industries,
Universal Amplitude Ratios in the Ising Model in Three Dimensions
We use a high-precision Monte Carlo simulation to determine the universal
specific-heat amplitude ratio A+/A- in the three-dimensional Ising model via
the impact angle \phi of complex temperature zeros. We also measure the
correlation-length critical exponent \nu from finite-size scaling, and the
specific-heat exponent \alpha through hyperscaling. Extrapolations to the
thermodynamic limit yield \phi = 59.2(1.0) degrees, A+/A- = 0.56(3), \nu =
0.63048(32) and \alpha = 0.1086(10). These results are compatible with some
previous estimates from a variety of sources and rule out recently conjectured
exact values.Comment: 17 pages, 5 figure
The Vertex-Face Correspondence and the Elliptic 6j-symbols
A new formula connecting the elliptic -symbols and the fusion of the
vertex-face intertwining vectors is given. This is based on the identification
of the fusion intertwining vectors with the change of base matrix elements
from Sklyanin's standard base to Rosengren's natural base in the space of even
theta functions of order . The new formula allows us to derive various
properties of the elliptic -symbols, such as the addition formula, the
biorthogonality property, the fusion formula and the Yang-Baxter relation. We
also discuss a connection with the Sklyanin algebra based on the factorised
formula for the -operator.Comment: 23 page
Identifying leverage points for strengthening adaptive capacity to climate change
Leverage points from systems research are increasingly important to understand how to support transformations towards sustainability, but few studies have considered leverage points in strengthening adaptive capacity to climate change. The existing literature mainly considers strengthening adaptive capacity as a steady and linear process. This article explores possibilities to fast track positive adaptive capacity trajectories of small-scale farmers in the Northern Region of Ghana. Leverage points were identified by triangulating data from semi-structured interviews with farmers (n=72), key informant interviews (n=7) and focus group discussions (FG1 n=17; FG2 n=20). The results present two ways to approach adaptation planning: 1) using four generic leverage points (gender equality, social learning, information and knowledge, and access to finance) or 2) combining the adaptive capacity and leverage point frameworks, thereby creating 15 associations. The generic points provide a set of topics as a starting point for policy and intervention planning activities, while the 15 associations support the identification of place-specific leverage points. Four benefits of using leverage points for adaptive capacity in adaptation planning were identified: guidance on where to intervene in a system, ability to deal with complex systems, inclusion of both causal and teleological decision-making, and a possibility to target deep, transformative change. Ā© 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.Peer reviewe
The Contributions of Vestibular Evoked Myogenic Potentials and Acoustic Vestibular Stimulation to Our Understanding of the Vestibular System
Vestibular-evoked myogenic potentials (VEMPs) are short-latency muscle reflexes typically recorded from the neck or eye muscles with surface electrodes. They are used clinically to assess otolith function, but are also interesting as they can provide information about the vestibular system and its activation by sound and vibration. Since the introduction of VEMPs more than 25 years ago, VEMPs have inspired animal and human research on the effects of acoustic vestibular stimulation on the vestibular organs, their projections and the postural muscles involved in vestibular reflexes. Using a combination of recording techniques, including single motor unit recordings, VEMP studies have enhanced our understanding of the excitability changes underlying the sound-evoked vestibulo-collic and vestibulo-ocular reflexes. Studies in patients with diseases of the vestibular system, such as superior canal dehiscence and Meniere's disease, have shown how acoustic vestibular stimulation is affected by physical changes in the vestibule, and how sound-evoked reflexes can detect these changes and their resolution in clinical contexts. This review outlines the advances in our understanding of the vestibular system that have occurred following the renewed interest in sound and vibration as a result of the VEMP
Influences of state anxiety on gaze behavior and stepping accuracy in older adults during adaptive locomotion
This article is available open access through the publisherās website at the link below. Copyright Ā© The Authors 2011.OBJECTIVES: Older adults deemed to be at a high risk of falling transfer their gaze from a stepping target earlier than their low-risk counterparts. The extent of premature gaze transfer increases with task complexity and is associated with a decline in stepping accuracy. This study tests the hypothesis that increased anxiety about upcoming obstacles is associated with (a) premature transfers of gaze toward obstacles (i.e., looking away from a target box prior to completing the step on it in order to fixate future constraints in the walkway) and (b) reduced stepping accuracy on the target in older adults. METHODS: High-risk (9) and low-risk (8) older adult participants walked a 10-m pathway containing a stepping target area followed by various arrangements of obstacles, which varied with each trial. Anxiety, eye movements, and movement kinematics were measured. RESULTS: Progressively increasing task complexity resulted in associated statistically significant increases in measures of anxiety, extent of early gaze transfer, and stepping inaccuracies in the high-risk group. DISCUSSION: These results provide evidence that increased anxiety about environmental hazards is related to suboptimal visual sampling behavior which, in turn, negatively influences stepping performance, potentially contributing to increased falls risk in older adults.Biotechnology and Biological Sciences Research Counci
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