1,605 research outputs found
Enhancing data locality by using terminal propagation
Terminal propagation is a method developed in the circuit placement community for adding constraints to graph partitioning problems. This paper adapts and expands this idea, and applies it to the problem of partitioning data structures among the processors of a parallel computer. We show how the constraints in terminal propagation can be used to encourage partitions in which messages are communicated only between architecturally near processors. We then show how these constraints can be handled in two important partitioning algorithms, spectral bisection and multilevel-KL. We compare the quality of partitions generated by these algorithms to each other and to Partitions generated by more familiar techniques
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Skewed graph partitioning
Graph partitioning is an important abstraction used in solving many scientific computing problems. Unfortunately, the standard partitioning model does not incorporate considerations that are important in many settings. We address this by describing a generalized partitioning model which incorporates the notion of partition skew and is applicable to a variety of problems. We then develop enhancements to several important partitioning algorithms necessary to solve the generalized partitioning problem. Finally we demonstrate the benefit of employing several of these generalized methods to static decomposition of parallel computing problems
Chemical solution deposition of multiferroic La0.7Sr0.3MnO3, BaTiO3 thin films prepared by ink plotting
Combinatorial synthesis of (YxGd1-x)Ba2Cu3Ox superconducting thin films
Environmentally friendly water-based YBa2Cu3Ox (YBCO) and GdBa2Cu3Ox (GdBCO) precursor solutions were synthesized to realize thin films by chemical solution deposition. Pure YBCO and GdBCO precursor solutions were used for ink plotting on SrTiO3 substrates and subsequent thermal treatment at the corresponding crystallization temperature. Phase formation of Gd123 requires a higher crystallization temperature of 840 °C compared to the Y123 phase. The critical temperature of YBCO films is about 92 K with a sharp transition into the superconducting state. Micro liter sized ink volumes of YBCO and GdBCO were successfully mixed for two-dimensional ink plotting of a (YxGd1-x)Ba2Cu3Ox film library. A homogeneous surface and no indication of a-axis growth were found in all mixed films
Chemical solution deposition of multiferroic La0.7Sr0.3MnO3, BaTiO3 thin films prepared by ink plotting
Global Stability of Infectious Disease Models Using Lyapunov Functions
Two systematic methods are presented to guide the construction of Lyapunov functions for general infectious disease models and are thus applicable to establish their global dynamics. Specifically, a matrix-theoretic method using the Perron eigenvector is applied to prove the global stability of the disease-free equilibrium, while a graph-theoretic method based on Kirchhoff\u27s matrix tree theorem and two new combinatorial identities are used to prove the global stability of the endemic equilibrium. Several disease models in the literature and two new cholera models are used to demonstrate the applications of these methods
A study on vaccination models for a seasonal epidemic process
In this paper seasonal epidemiological processes are considered and a strategy of periodic vaccination is proposed. The invariant formulations associated with an N-periodic system and the reproduction numbers associated with them are considered. A collection of measures to study the stability of the system is introduced. Moreover, the collection of s-basic reproduction number at time j help us to establish conditions on the periodic vaccination rates in the vaccination program. Finally, an SIR model is showed and a comparison between the results obtained using constant or periodic vaccination program is analyzed. (C) 2014 Elsevier Inc. All rights reserved.The authors wish to express their thanks to the reviewers for helpful comments and suggestions. This paper is supported by Grant MTM2010-18228.Cantó Colomina, B.; Coll, C.; Sánchez, E. (2014). A study on vaccination models for a seasonal epidemic process. Applied Mathematics and Computation. 243:152-160. https://doi.org/10.1016/j.amc.2014.05.104S15216024
Cyclosporine A reduces microvascular obstruction and preserves left ventricular function deterioration following myocardial ischemia and reperfusion
Postconditioning and cyclosporine A prevent
mitochondrial permeability transition pore opening providing
cardioprotection during ischemia/reperfusion.
Whether microvascular obstruction is affected by these
interventions is largely unknown. Pigs subjected to coronary
occlusion for 1 h followed by 3 h of reperfusion were
assigned to control (n = 8), postconditioning (n = 9) or
cyclosporine A intravenous infusion 10-15 min before the
end of ischemia (n = 8). Postconditioning was induced by
8 cycles of repeated 30-s balloon inflation and deflation.
After 3 h of reperfusion magnetic resonance imaging,
triphenyltetrazolium chloride/Evans blue staining and histopathology
were performed. Microvascular obstruction
(MVO, percentage of gadolinium-hyperenhanced area) was
measured early (3 min) and late (12 min) after contrast
injection. Infarct size with double staining was smaller in
cyclosporine (46.2 ± 3.1 %, P = 0.016) and postconditioning
pigs (47.6 ± 3.9 %, P = 0.008) versus controls
(53.8 ± 4.1 %). Late MVO was significantly reduced by
cyclosporine (13.9 ± 9.6 %, P = 0.047) but not postconditioning
(23.6 ± 11.7 %, P = 0.66) when compared with
controls (32.0 ± 16.9 %). Myocardial blood flow in the
late MVO was improved with cyclosporine versus controls
(0.30 ± 0.06 vs 0.21 ± 0.03 ml/g/min, P = 0.002) and
was inversely correlated with late-MVO extent ( = 0.93,
P\0.0001). Deterioration of left ventricular ejection
fraction (LVEF) between baseline and 3 h of reperfusion
was smaller with cyclosporine (-7.9 ± 2.4 %, P = 0.008)
but not postconditioning (-12.0 ± 5.5 %, P = 0.22) when
compared with controls (-16.4 ± 5.5 %). In the three
groups, infarct size (\beta = -0.69, P\0.001) and late MVO
(\beta = -0.33, P = 0.02) were independent predictors of
LVEF deterioration following ischemia/reperfusion
(R^{2} = 0.73, P\0.001). Despite both cyclosporine A and
postconditioning reduce infarct size, only cyclosporine A
infusion had a beneficial effect on microvascular damage
and was associated with better preserved LV function when
compared with controls
From regional pulse vaccination to global disease eradication: insights from a mathematical model of Poliomyelitis
Mass-vaccination campaigns are an important strategy in the global fight
against poliomyelitis and measles. The large-scale logistics required for these
mass immunisation campaigns magnifies the need for research into the
effectiveness and optimal deployment of pulse vaccination. In order to better
understand this control strategy, we propose a mathematical model accounting
for the disease dynamics in connected regions, incorporating seasonality,
environmental reservoirs and independent periodic pulse vaccination schedules
in each region. The effective reproduction number, , is defined and proved
to be a global threshold for persistence of the disease. Analytical and
numerical calculations show the importance of synchronising the pulse
vaccinations in connected regions and the timing of the pulses with respect to
the pathogen circulation seasonality. Our results indicate that it may be
crucial for mass-vaccination programs, such as national immunisation days, to
be synchronised across different regions. In addition, simulations show that a
migration imbalance can increase and alter how pulse vaccination should
be optimally distributed among the patches, similar to results found with
constant-rate vaccination. Furthermore, contrary to the case of constant-rate
vaccination, the fraction of environmental transmission affects the value of
when pulse vaccination is present.Comment: Added section 6.1, made other revisions, changed titl
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