Exploring probabilistic grammars of symbolic music using PRISM

In this paper we describe how we used the logic-based probabilistic programming language PRISM to conduct a systematic comparison of several probabilistic models of symbolic music, including 0th and 1st order Markov models over pitches and intervals, and a probabilistic grammar with two parameterisations. Using PRISM allows us to take advantage of variational Bayesian methods for assessing the goodness of fit of the models. When applied to a corpus of Bach chorales and the Essen folk song collection, we found that, depending on various parameters, the probabilistic grammars sometimes but not always out-perform the simple Markov models. Examining how the models perform on smaller subsets of pieces, we find that the simpler Markov models do out-perform the best grammar-based model at the small end of the scale

Comparing models of symbolic music using probabilistic grammars and probabilistic programming

We conduct a systematic comparison of several probabilistic models of symbolic music, including zeroth and first order Markov models over pitches and intervals, a hidden Markov model over pitches, and a probabilistic context free grammar with two parameterisations, all implemented uniformly using a probabilistic programming language (PRISM). This allows us to take advantage of variational Bayesian methods for learning parameters and assessing the goodness of fit of the models in a principled way. When applied to a corpus of Bach chorales and the Essen folk song collection, we show that, depending on various parameters, the probabilistic grammars sometimes but not always out-perform the simple Markov models. On looking for evidence of over- fitting of complex models to small datasets, we find that even the smallest dataset is sufficient to support the richest parameterisation of the probabilistic grammars. However, examining how the models perform on smaller subsets of pieces, we find that the simpler Markov models do indeed out-perform the best grammar-based model at the small end of the scale

Classifying the Arithmetical Complexity of Teaching Models

This paper classifies the complexity of various teaching models by their position in the arithmetical hierarchy. In particular, we determine the arithmetical complexity of the index sets of the following classes: (1) the class of uniformly r.e. families with finite teaching dimension, and (2) the class of uniformly r.e. families with finite positive recursive teaching dimension witnessed by a uniformly r.e. teaching sequence. We also derive the arithmetical complexity of several other decision problems in teaching, such as the problem of deciding, given an effective coding $\{\mathcal L_0,\mathcal L_1,\mathcal L_2,\ldots\}$ of all uniformly r.e. families, any $e$ such that $\mathcal L_e = \{L^e_0,L^e_1,\ldots,\}$, any $i$ and $d$, whether or not the teaching dimension of $L^e_i$ with respect to $\mathcal L_e$ is upper bounded by $d$.Comment: 15 pages in International Conference on Algorithmic Learning Theory, 201

Compression-based Dependencies Among Rhythmic Motifs in a Score

Music similarity has been widely studied through melodic and harmonic matching, clustering, and using various metrics for measuring distance. Such analyses offer the musicologist a view of the ‘sameness’ of parts of a score. However, similarity alone does not necessarily allow exploitation of that sameness in reasoning about the music. In this paper, we present work in progress to investigate rhythm similarity at various scales, beginning at the smallest (single measures or groups of measures). We use normalised compression distance and variations thereof to derive similarity-based dependencies between parts of the music. Establishing such dependencies may allow software engineering dependence analysis techniques to be applied to music to, e.g. remove from focus aspects not relevant to a particular enquiry (‘slicing’), determine the sensitivity of later parts of the music on former parts (‘impact analysis’), and to find motivic processes and developments within the musical form. The analysis will thus draw on software engineering techniques, information theory, and data compression. Our results thus far show that text-based compressors introduce significant non-linear artefacts at small scales making similarity identification based on compressed lengths difficult. Future work will involve progressively larger scale music to determine the sensitivity of the results to the size of music being analysed in order to guide musicologists wanting to adopt similar approaches. We expect to find that at larger scales, the artefacts in text compression become less significant and identifying the threshold at which this happens is thus important. We discuss tree compression as having the potential to capture musically-important relationships lost by text compression and believe that this approach would be more successful at small scales

A descriptive study of chiropractors' opinions and practices regarding office-based health product sales

<p>Abstract</p> <p>Background</p> <p>Although the sale of non-prescription health products is ubiquitous, the views of health professionals, such as chiropractors, regarding the sale of such products are not well known. Practitioner opinion is important to understand and inform professional practice. The purpose of this study was to describe chiropractors' perspectives and practices on the sale of health care products from practitioners' offices.</p> <p>Methods</p> <p>Chiropractors were invited to provide written comments about health product sales at the end of a fixed choice, mailed survey. Respondents' comments were analyzed using qualitative description. Ethics approval was received from the Conjoint Health Research Ethics Board at the University of Calgary.</p> <p>Results</p> <p>One hundred seven of the 265 respondents (response rate of 51%) provided written comments. Approximately 30 pages of double-spaced, typed text were gathered. Respondents did not consistently endorse or condemn health product sales, and engaged in the practice to greater and lesser extents. While some were opposed to health products sales, some accepted the practice with a degree of ambivalence whereas others clearly embraced it. Some respondents acknowledged a professional conflict of interest in such sales and marketing, and described strategies used to mitigate it. Others provided a range of justifications for the practice. Personal integrity and professional standards were discussed and a need for monitoring identified.</p> <p>Conclusions</p> <p>A wide range of opinions and practices were described and this is consistent with resulting variation in practice. In light of this, standards that facilitate consistency in practice may benefit professionals and the public alike.</p

Mass Sport Through Education or Elite Olympic Sport?

xxi, 274 hlm,; ilus.; 25 cm

Chylous ascites and chylothorax: a case study

No Abstract.&nbsp

Detecting the orientation of magnetic fields in galaxy clusters

Clusters of galaxies, filled with hot magnetized plasma, are the largest bound objects in existence and an important touchstone in understanding the formation of structures in our Universe. In such clusters, thermal conduction follows field lines, so magnetic fields strongly shape the cluster's thermal history; that some have not since cooled and collapsed is a mystery. In a seemingly unrelated puzzle, recent observations of Virgo cluster spiral galaxies imply ridges of strong, coherent magnetic fields offset from their centre. Here we demonstrate, using three-dimensional magnetohydrodynamical simulations, that such ridges are easily explained by galaxies sweeping up field lines as they orbit inside the cluster. This magnetic drape is then lit up with cosmic rays from the galaxies' stars, generating coherent polarized emission at the galaxies' leading edges. This immediately presents a technique for probing local orientations and characteristic length scales of cluster magnetic fields. The first application of this technique, mapping the field of the Virgo cluster, gives a startling result: outside a central region, the magnetic field is preferentially oriented radially as predicted by the magnetothermal instability. Our results strongly suggest a mechanism for maintaining some clusters in a 'non-cooling-core' state.Comment: 48 pages, 21 figures, revised version to match published article in Nature Physics, high-resolution version available at http://www.cita.utoronto.ca/~pfrommer/Publications/pfrommer-dursi.pd

Neutron Stars in Teleparallel Gravity

In this paper we deal with neutron stars, which are described by a perfect fluid model, in the context of the teleparallel equivalent of general relativity. We use numerical simulations to find the relationship between the angular momentum of the field and the angular momentum of the source. Such a relation was established for each stable star reached by the numerical simulation once the code is fed with an equation of state, the central energy density and the ratio between polar and equatorial radii. We also find a regime where linear relation between gravitational angular momentum and moment of inertia (as well as angular velocity of the fluid) is valid. We give the spatial distribution of the gravitational energy and show that it has a linear dependence with the squared angular velocity of the source.Comment: 19 pages, 14 figures. arXiv admin note: text overlap with arXiv:1206.331

High Adherence Is Necessary to Realize Health Gains from Water Quality Interventions

BACKGROUND: Safe drinking water is critical for health. Household water treatment (HWT) has been recommended for improving access to potable water where existing sources are unsafe. Reports of low adherence to HWT may limit the usefulness of this approach, however. METHODS AND FINDINGS: We constructed a quantitative microbial risk model to predict gains in health attributable to water quality interventions based on a range of assumptions about pre-treatment water quality; treatment effectiveness in reducing bacteria, viruses, and protozoan parasites; adherence to treatment interventions; volume of water consumed per person per day; and other variables. According to mean estimates, greater than 500 DALYs may be averted per 100,000 person-years with increased access to safe water, assuming moderately poor pre-treatment water quality that is a source of risk and high treatment adherence (>90% of water consumed is treated). A decline in adherence from 100% to 90% reduces predicted health gains by up to 96%, with sharpest declines when pre-treatment water quality is of higher risk. CONCLUSIONS: Results suggest that high adherence is essential in order to realize potential health gains from HWT