782 research outputs found

    Extinction transitions in correlated external noise

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    We analyze the influence of long-range correlated (colored) external noise on extinction phase transitions in growth and spreading processes. Uncorrelated environmental noise (i.e., temporal disorder) was recently shown to give rise to an unusual infinite-noise critical point [Europhys. Lett. 112, 30002 (2015)]. It is characterized by enormous density fluctuations that increase without limit at criticality. As a result, a typical population decays much faster than the ensemble average which is dominated by rare events. Using the logistic evolution equation as an example, we show here that positively correlated (red) environmental noise further enhances these effects. This means, the correlations accelerate the decay of a typical population but slow down the decay of the ensemble average. Moreover, the mean time to extinction of a population in the active, surviving phase grows slower than a power law with population size. To determine the complete critical behavior of the extinction transition, we establish a relation to fractional random walks, and we perform extensive Monte-Carlo simulations.Comment: 11 pages, 12 figures, Final versio

    Predicting Global Disposition of U.S. Military Personnel via Open-Source, Unclassified Means

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    The Joint Distribution Processing Analysis Center (JDPAC) of the United States Transportation Command (USTRANSCOM) regularly forecasts the demand of USTRANSCOM assets required by geographic and combatant commanders. These demands are subject to fluctuations due to unforeseen circumstances such as war, conflict, natural disasters, and other calamities requiring the presence of military personnel. This study evaluates the use of exponential state space smoothing, ARIMA, and Regression with ARIMA errors models to forecast the number of military personnel expected in each country, for a test set of countries of interest to USTRANSCOM and which manifest a high degree of variability in the anticipated number of troops each year. The expectation by USTRANSCOM is that accurate forecasts for the number of military personnel in each country can be leveraged to develop alternative transportation workload forecasts of demand of USTRANSCOM assets. There was not a single model that performed best for all countries and branches of service. Each model was analyzed via the traditional 80/20 forecasting evaluation metric as well as a two-year horizon cross-validation metric. The exponential smoothing model with a high level of α performed quite well for many of the models, indicating that perhaps simpler models will still provide accurate forecasts. Further research is needed to determine whether incorporating forecasts of military personnel will improve the ability to forecast demand of USTRANSCOM assets

    Imagination as Thought in Aristotle\u27s De Anima

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    Aristotle appears to indicate in various passages in the De Anima that imagination is a kind of thought, and my thesis attempts to make some sense out of this claim. I examine three possible interpretations of the claim that imagination is a kind of thought and eliminate two of them. The first states that Aristotle only calls imagination a kind of thought in a superficial “in name only” sense. The second, more radical interpretation, identifies images as the most basic kind of thoughts. My final chapter defends a more moderate position—inspired by Avempace and the early Averroes—which steers between the superficial and radical interpretations, by construing the formal content of images as a sort of quasi-corporeal substrate for the generation of learned thoughts

    Extinction Transitions in Correlated External Noise

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    We analyze the influence of long-range correlated (colored) external noise on extinction phase transitions in growth and spreading processes. Uncorrelated environmental noise (i.e., temporal disorder) was recently shown to give rise to an unusual infinite-noise critical point [Europhys. Lett. 112, 30002 (2015)EULEEJ0295-507510.1209/0295-5075/112/30002]. It is characterized by enormous density fluctuations that increase without limit at criticality. As a result, a typical population decays much faster than the ensemble average, which is dominated by rare events. Using the logistic evolution equation as an example, we show here that positively correlated (red) environmental noise further enhances these effects. This means, the correlations accelerate the decay of a typical population but slow down the decay of the ensemble average. Moreover, the mean time to extinction of a population in the active, surviving phase grows slower than a power law with population size. To determine the complete critical behavior of the extinction transition, we establish a relation to fractional random walks, and we perform extensive Monte Carlo simulations

    Albania Project Center Resource Development

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    The purpose of the project was to develop resources for students and sponsors who are or may be participating in the Albania Project Center in future years. We developed a website, together with a blog and photo gallery, and we considered potential project topics and suggested relevant contacts. Information was gathered from web sources as well as through personal interviews and discussions. This report explains the process of the project as well as the reasoning behind the team’s decisions

    A haplome alignment and reference sequence of the highly polymorphic Ciona savignyi genome

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    The high degree of polymorphism in the genome of the sea squirt Ciona savignyi complicated the assembly of sequence contigs, but a new alignment method results in a much improved sequence

    Burn Rate Sensitization of Solid Propellants Using A Nano-Titania Additive

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    Adding nanoparticles as a catalyst to solid propellant fuel to increase and enhance burn rates of the fuel by up to 10 times or more and or modifying the pressure index. A preferred embodiment uses titanium dioxide nanoparticles mixed with a solid propellant fuel, where the nanoparticles are approximately 2% or less of total propellant mixture. The high surface to volume ratio of the nanoparticles improve the performance of the solid propellant fuel

    Burn Rate Sensitization of Solid Propellants Using A Nano-Titania Additive

    Get PDF
    Adding nanoparticles as a catalyst to solid propellant fuel to increase and enhance burn rates of the fuel by up to 10 times or more and or modifying the pressure index. A preferred embodiment uses titanium dioxide nanoparticles mixed with a solid propellant fuel, where the nanoparticles are approximately 2% or less of total propellant mixture. The high surface to volume ratio of the nanoparticles improve the performance of the solid propellant fuel

    Molecularly Imprinted Solid Phase Extraction of Taxanes from Plant Cell Culture

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    Paclitaxel is a taxane used to combat various forms of cancer. Formed in suspension cultures with other taxanes, purifying paclitaxel is difficult because most taxanes have a chemically similar structure. Molecularly imprinted polymers (MIPs) are artificial receptors that have the potential to alleviate this problem because they are engineered to selectively bind to target molecules. The goals of this project were to determine the optimum conditions for producing paclitaxel-specific MIPs and test their effectiveness in separating paclitaxel from a mixture of other taxanes. Based on various experiments, our group was able to produce MIPs that bound to 70% of paclitaxel in a 10 mg/L solution and proposed recommendations to produce more effective MIPs in the future
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