301 research outputs found
Asymptotic structure of cosmological fluid flows in one and two space dimensions: a numerical study
We consider an isothermal compressible fluid evolving on a cosmological
background which may be either expanding or contracting toward the future. The
Euler equations governing such a flow consist of two nonlinear hyperbolic
balance laws which we treat in one and in two space dimensions. We design a
finite volume scheme which is fourth-order accurate in time and second-order
accurate in space. This scheme allows us to compute weak solutions containing
shock waves and, by design, is well-balanced in the sense that it preserves
exactly a special class of solutions. Using this scheme, we investigate the
asymptotic structure of the fluid when the time variable approaches infinity
(in the expanding regime) or approaches zero (in the contracting regime). We
study these two limits by introducing a suitable rescaling of the density and
velocity variables and, in turn, we analyze the effects induced by the
geometric terms (of expanding or contracting nature) and the nonlinear
interactions between shocks. Extensive numerical experiments in one and in two
space dimensions are performed in order to support our observations.Comment: 41 page
Interacting Adaptive Processes with Different Timescales Underlie Short-Term Motor Learning
Multiple processes may contribute to motor skill acquisition, but it is thought that many of these processes require sleep or the passage of long periods of time ranging from several hours to many days or weeks. Here we demonstrate that within a timescale of minutes, two distinct fast-acting processes drive motor adaptation. One process responds weakly to error but retains information well, whereas the other responds strongly but has poor retention. This two-state learning system makes the surprising prediction of spontaneous recovery (or adaptation rebound) if error feedback is clamped at zero following an adaptation-extinction training episode. We used a novel paradigm to experimentally confirm this prediction in human motor learning of reaching, and we show that the interaction between the learning processes in this simple two-state system provides a unifying explanation for several different, apparently unrelated, phenomena in motor adaptation including savings, anterograde interference, spontaneous recovery, and rapid unlearning. Our results suggest that motor adaptation depends on at least two distinct neural systems that have different sensitivity to error and retain information at different rates
Information needs of managers and expert panels in the office of disaster management and emergency medical services in Iran�s ministry of health and medical education
Background and purpose: The office of disaster management and emergency medical service is one of the most important subdivisions of the Ministry of health. Analyzing the tasks and functions of this office is critical to its evaluation. This study aimed at analyzing the information needs of this office to develop statistical indicators required. Materials and methods: This qualitative-quantitative study was carried out during 2015. The study population included the managers and expert panels in disaster management and emergency medical service in the Ministry of Health and Medical Education of Iran. We interviewed 14 individuals in different departments within the office and reviewed the administrative tasks and the available documents. After analyzing the data, different information needs of all departments were identified and classified. Results: According to the administrative tasks and practices, 69 groups of information needs were identified of which 17.4 are not met. 45.3 of the information needs did not have any standard sources or forms to collect the data required. Conclusion: Lack of standard sources for the most identified information needs, decentralized information systems, and out-of-date information are the major problems of managers and expert panels. So, designing national standard forms to collect data, designing a comprehensive statistics and information system and reviewing current paper forms and databases seem to be essential. © 2016, Mazandaran University of Medical Sciences. All rights reserved
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Sustainable and inclusive demand-side resilience: a semi-dynamic model for outage costs
The power system is primarily designed and concerned with supplying electricity to its customers at all times. Nevertheless, power outages are inevitable; therefore, one of the challenges is to accurately determine the costs and damages to consumers in a fair and inclusive manner. Outage events are regularly costed based on a parameter called the Value of Lost Load (VoLL/VOLL). Although some of the influencing factors on outage costs have been identified in the literature, the exact determination of the damage to customers is still considered a big challenge. This work is an effort toward a more sustainable and inclusive demand-side resilience that provides a semi-dynamic model for the assignment of the power outage damage costs to the customers. The results of the proposed method show how using a semi-dynamic model for outage costs leads to more sustainable and inclusive operating decisions in the power system while also leads to a fairer allocation of costs
Genetic determinants of premature menopause in A Mashhad population cohort
Funding Information: This work was supported by a grant from the Vice Chancellor for Research at Mashhad University of Medical Sciences and this was a part of the Ph.D. student dissertation (no. 971084). The authors have no conflict of interest to disclose.Peer reviewedPublisher PD
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