188 research outputs found
Chaos in a Two-Dimensional Ising Spin Glass
We study chaos in a two dimensional Ising spin glass by finite temperature
Monte Carlo simulations. We are able to detect chaos with respect to
temperature changes as well as chaos with respect to changing the bonds, and
find that the chaos exponents for these two cases are equal. Our value for the
exponent appears to be consistent with that obtained in studies at zero
temperature.Comment: 4 pages, LaTeX, 4 postscript figures included. The analysis of the
data is now done somewhat differently. The results are consistent with the
chaos exponent found at zero temperature. Additional papers of PY can be
obtained on-line at http://schubert.ucsc.edu/pete
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
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
Time reparametrization group and the long time behaviour in quantum glassy systems
We study the long time dynamics of a quantum version of the
Sherrington-Kirkpatrick model. Time reparametrizations of the dynamical
equations have a parallel with renormalization group transformations, and
within this language the long time behaviour of this model is controlled by a
reparametrization group (RG) fixed point of the classical dynamics. The
irrelevance of the quantum terms in the dynamical equations in the aging regime
explains the classical nature of the violation of the fluctuation-dissipation
theorem.Comment: 4 page
Organizational and Supervisory Apology Effectiveness: Apology Giving in Work Settings
We synthesize the interdisciplinary literature into a heuristic for crafting effective organizational and supervisory apologies (the OOPS four-component apology). In the first experiment, we demonstrate how an offense committed by an organization is perceived to be more egregious than an offense committed by a friend or supervisor. Furthermore, results did not support that OOPS apologies are unequally effective if issued by a friend, supervisor, or organization. In the second experiment, we test OOPS apology-training effectiveness. Results indicated that trained participants crafted more effective apologies. Our apology heuristic is an innovation for training business communicators how to apologize effectively.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Modeling the Development of Goal-Specificity in Mirror Neurons
Neurophysiological studies have shown that parietal mirror neurons encode not only actions but also the goal of these actions. Although some mirror neurons will fire whenever a certain action is perceived (goal-independently), most will only fire if the motion is perceived as part of an action with a specific goal. This result is important for the action-understanding hypothesis as it provides a potential neurological basis for such a cognitive ability. It is also relevant for the design of artificial cognitive systems, in particular robotic systems that rely on computational models of the mirror system in their interaction with other agents. Yet, to date, no computational model has explicitly addressed the mechanisms that give rise to both goal-specific and goal-independent parietal mirror neurons. In the present paper, we present a computational model based on a self-organizing map, which receives artificial inputs representing information about both the observed or executed actions and the context in which they were executed. We show that the map develops a biologically plausible organization in which goal-specific mirror neurons emerge. We further show that the fundamental cause for both the appearance and the number of goal-specific neurons can be found in geometric relationships between the different inputs to the map. The results are important to the action-understanding hypothesis as they provide a mechanism for the emergence of goal-specific parietal mirror neurons and lead to a number of predictions: (1) Learning of new goals may mostly reassign existing goal-specific neurons rather than recruit new ones; (2) input differences between executed and observed actions can explain observed corresponding differences in the number of goal-specific neurons; and (3) the percentage of goal-specific neurons may differ between motion primitives
Quantum Griffiths effects and smeared phase transitions in metals: theory and experiment
In this paper, we review theoretical and experimental research on rare region
effects at quantum phase transitions in disordered itinerant electron systems.
After summarizing a few basic concepts about phase transitions in the presence
of quenched randomness, we introduce the idea of rare regions and discuss their
importance. We then analyze in detail the different phenomena that can arise at
magnetic quantum phase transitions in disordered metals, including quantum
Griffiths singularities, smeared phase transitions, and cluster-glass
formation. For each scenario, we discuss the resulting phase diagram and
summarize the behavior of various observables. We then review several recent
experiments that provide examples of these rare region phenomena. We conclude
by discussing limitations of current approaches and open questions.Comment: 31 pages, 7 eps figures included, v2: discussion of the dissipative
Ising chain fixed, references added, v3: final version as publishe
Non invasive ventilation after extubation in paediatric patients: a preliminary study
<p>Abstract</p> <p>Background</p> <p>Non-invasive ventilation (NIV) may be useful after extubation in children. Our objective was to determine postextubation NIV characteristics and to identify risk factors of postextubation NIV failure.</p> <p>Methods</p> <p>A prospective observational study was conducted in an 8-bed pediatric intensive care unit (PICU). Following PICU protocol, NIV was applied to patients who had been mechanically ventilated for over 12 hours considered at high-risk of extubation failure -elective NIV (eNIV), immediately after extubation- or those who developed respiratory failure within 48 hours after extubation -rescue NIV (rNIV)-. Patients were categorized in subgroups according to their main underlying conditions. NIV was deemed successful when reintubation was avoided. Logistic regression analysis was performed in order to identify predictors of NIV failure.</p> <p>Results</p> <p>There were 41 episodes (rNIV in 20 episodes). Success rate was 50% in rNIV and 81% in eNIV (p = 0.037). We found significant differences in univariate analysis between success and failure groups in respiratory rate (RR) decrease at 6 hours, FiO<sub>2 </sub>at 1 hour and PO<sub>2</sub>/FiO<sub>2 </sub>ratio at 6 hours. Neurologic condition was found to be associated with NIV failure. Multiple logistic regression analysis identified no variable as independent NIV outcome predictor.</p> <p>Conclusions</p> <p>Our data suggest that postextubation NIV seems to be useful in avoiding reintubation in high-risk children when applied immediately after extubation. NIV was more likely to fail when ARF has already developed (rNIV), when RR at 6 hours did not decrease and if oxygen requirements increased. Neurologic patients seem to be at higher risk of reintubation despite NIV use.</p
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