1,135 research outputs found
Simplifying asteroseismic analysis of solar-like oscillators: An application of principal component analysis for dimensionality reduction
The asteroseismic analysis of stellar power density spectra is often
computationally expensive. The models used in the analysis may use several
dozen parameters to accurately describe features in the spectra caused by
oscillation modes and surface granulation. Many parameters are often highly
correlated, making the parameter space difficult to quickly and accurately
sample. They are, however, all dependent on a smaller set of parameters, namely
the fundamental stellar properties. We aim to leverage this to simplify the
process of sampling the model parameter space for the asteroseismic analysis of
solar-like oscillators, with an emphasis on mode identification. Using a large
set of previous observations, we applied principal component analysis to the
sample covariance matrix to select a new basis on which to sample the model
parameters. Selecting the subset of basis vectors that explains the majority of
the sample variance, we redefine the model parameter prior probability density
distributions in terms of a smaller set of latent parameters. We are able to
reduce the dimensionality of the sampled parameter space by a factor of two to
three. The number of latent parameters needed to accurately model the stellar
oscillation spectra cannot be determined exactly but is likely only between
four and six. Using two latent parameters, the method is able to describe the
bulk features of the oscillation spectrum, while including more latent
parameters allows for a frequency precision better than of the
small frequency separation for a given target. We find that sampling a
lower-rank latent parameter space still allows for accurate mode identification
and parameter estimation on solar-like oscillators over a wide range of
evolutionary stages. This allows for the potential to increase the complexity
of spectrum models without a corresponding increase in computational expense.Comment: Accepted for publication in Astronomy & Astrophysics. 11 pages. 10
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Bayesian Conditioning, the Reflection Principle, and Quantum Decoherence
The probabilities a Bayesian agent assigns to a set of events typically
change with time, for instance when the agent updates them in the light of new
data. In this paper we address the question of how an agent's probabilities at
different times are constrained by Dutch-book coherence. We review and attempt
to clarify the argument that, although an agent is not forced by coherence to
use the usual Bayesian conditioning rule to update his probabilities, coherence
does require the agent's probabilities to satisfy van Fraassen's [1984]
reflection principle (which entails a related constraint pointed out by
Goldstein [1983]). We then exhibit the specialized assumption needed to recover
Bayesian conditioning from an analogous reflection-style consideration.
Bringing the argument to the context of quantum measurement theory, we show
that "quantum decoherence" can be understood in purely personalist
terms---quantum decoherence (as supposed in a von Neumann chain) is not a
physical process at all, but an application of the reflection principle. From
this point of view, the decoherence theory of Zeh, Zurek, and others as a story
of quantum measurement has the plot turned exactly backward.Comment: 14 pages, written in memory of Itamar Pitowsk
Current Dyspnea Among Long-Term Survivors of Early-Stage Non-small Cell Lung Cancer
IntroductionDyspnea is common among lung cancer patients. As most studies of dyspnea have reviewed patients with active cancer or immediately after treatment, its prevalence during the longer-term period once treatment has been completed is not well characterized. This study quantifies the prevalence of dyspnea among lung cancer survivors and identifies potential correlates that may be amenable to intervention.MethodsCross-sectional survey of 342 patients with disease-free, stage I, non-small cell lung cancer, assessed 1 to 6 years after surgical resection. Dyspnea was quantified using the Baseline Dyspnea Index. Any moderate/strenuous physical activity was measured using the Godin Leisure-Time Exercise Questionnaire. Mood disorder symptoms were assessed using the Hospital Anxiety and Depression Scale. Multiple regression analyses were used to examine demographic, medical, and health-related correlates of dyspnea.ResultsMean age was 68.9 years. Average predicted preoperative forced expiratory volume in 1 second was 89.0%. Current dyspnea, defined by a Baseline Dyspnea Index score of 9 or less, existed among 205 (60%) individuals. For 133 (65%) of these patients, dyspnea was absent preoperatively. Multivariate correlates of current dyspnea included preoperative dyspnea (odds ratio [OR] = 5.31), preoperative diffusing capacity (OR = 0.98), lack of moderate/strenuous physical activity (OR = 0.41), and the presence of clinically significant depression symptoms (OR = 4.10).ConclusionsDyspnea is common 1 to 6 years after lung cancer resection, and is associated with the presence of preoperative dyspnea, reduced diffusing capacity, clinically significant depression symptoms, and lack of physical activity. Further research is needed to test whether strategies that identify and treat patients with these conditions attenuate dyspnea among lung cancer survivors
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Income-tested health entitlements: microsimulation modelling using SILC
The application of microsimulation techniques to tax and welfare policies is well established in many countries, including Ireland. The richness of the data contained in SILC, the CSO’s Survey on Income and Living Conditions, means that similar methods can also be applied to the analysis of policy in some other key areas. Income-tested health entitlements, which include most medical cards and many GP visit cards, are a major feature of the Irish health system. We examine how the income tests for such schemes can be modelled using the detailed income and demographic information in the CSO Survey on Income and Living Conditions. The ESRI’s SWITCH model is extended to apply the rules for income-related cards to each family in this nationally representative sample. A key issue which emerges is the apparently low level of take up among those entitled to GP visit cards. This has implications for the costing of policy changes, such as a shift to Universal Health Insurance (UHI) or widening of the age bands qualifying for non-income tested GP visit cards
A Quantum-Bayesian Route to Quantum-State Space
In the quantum-Bayesian approach to quantum foundations, a quantum state is
viewed as an expression of an agent's personalist Bayesian degrees of belief,
or probabilities, concerning the results of measurements. These probabilities
obey the usual probability rules as required by Dutch-book coherence, but
quantum mechanics imposes additional constraints upon them. In this paper, we
explore the question of deriving the structure of quantum-state space from a
set of assumptions in the spirit of quantum Bayesianism. The starting point is
the representation of quantum states induced by a symmetric informationally
complete measurement or SIC. In this representation, the Born rule takes the
form of a particularly simple modification of the law of total probability. We
show how to derive key features of quantum-state space from (i) the requirement
that the Born rule arises as a simple modification of the law of total
probability and (ii) a limited number of additional assumptions of a strong
Bayesian flavor.Comment: 7 pages, 1 figure, to appear in Foundations of Physics; this is a
condensation of the argument in arXiv:0906.2187v1 [quant-ph], with special
attention paid to making all assumptions explici
Oropouche virus cases identified in Ecuador using an optimised qRT-PCR informed by metagenomic sequencing
Oropouche virus (OROV) is responsible for outbreaks of Oropouche fever in parts of South America. We recently identified and isolated OROV from a febrile Ecuadorian patient, however, a previously published qRT-PCR assay did not detect OROV in the patient sample. A primer mismatch to the Ecuadorian OROV lineage was identified from metagenomic sequencing data. We report the optimisation of an qRT-PCR assay for the Ecuadorian OROV lineage, which subsequently identified a further five cases in a cohort of 196 febrile patients. We isolated OROV via cell culture and developed an algorithmically-designed primer set for whole-genome amplification of the virus. Metagenomic sequencing of the patient samples provided OROV genome coverage ranging from 68-99%. The additional cases formed a single phylogenetic cluster together with the initial case. OROV should be considered as a differential diagnosis for Ecuadorian patients with febrile illness to avoid mis-diagnosis with other circulating pathogens
Why We Ventilate
ABSTRACT It is widely accepted that ventilation is critical for providing good indoor air quality (IAQ) in homes. However, the definition of "good" IAQ, and the most effective, energy efficient methods for delivering it are still matters of research and debate. This paper presents the results of work done at the Lawrence Berkeley National Lab to identify the air pollutants that drive the need for ventilation as part of a larger effort to develop a health-based ventilation standard. First, we present results of a hazard analysis that identified the pollutants that most commonly reach concentrations in homes that exceed health-based standards or guidelines for chronic or acute exposures. Second, we present results of an impact assessment that identified the air pollutants that cause the most harm to the U.S. population from chronic inhalation in residences. Lastly, we describe the implications of our findings for developing effective ventilation standards
Behavioural syndrome in a solitary predator is independent of body size and growth rate.
Models explaining behavioural syndromes often focus on state-dependency, linking behavioural variation to individual differences in other phenotypic features. Empirical studies are, however, rare. Here, we tested for a size and growth-dependent stable behavioural syndrome in the juvenile-stages of a solitary apex predator (pike, Esox lucius), shown as repeatable foraging behaviour across risk. Pike swimming activity, latency to prey attack, number of successful and unsuccessful prey attacks was measured during the presence/absence of visual contact with a competitor or predator. Foraging behaviour across risks was considered an appropriate indicator of boldness in this solitary predator where a trade-off between foraging behaviour and threat avoidance has been reported. Support was found for a behavioural syndrome, where the rank order differences in the foraging behaviour between individuals were maintained across time and risk situation. However, individual behaviour was independent of body size and growth in conditions of high food availability, showing no evidence to support the state-dependent personality hypothesis. The importance of a combination of spatial and temporal environmental variation for generating growth differences is highlighted
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