Potential isomorphism of elementary substructures of a strictly stable homogeneous model

"Vegeu el resum a l'inici del document del fitxer adjunt"

A computational study on outliers in world music

The comparative analysis of world music cultures has been the focus of several ethnomusicological studies in the last century. With the advances of Music Information Retrieval and the increased accessibility of sound archives, large-scale analysis of world music with computational tools is today feasible. We investigate music similarity in a corpus of 8200 recordings of folk and traditional music from 137 countries around the world. In particular, we aim to identify music recordings that are most distinct compared to the rest of our corpus. We refer to these recordings as ‘outliers’. We use signal processing tools to extract music information from audio recordings, data mining to quantify similarity and detect outliers, and spatial statistics to account for geographical correlation. Our findings suggest that Botswana is the country with the most distinct recordings in the corpus and China is the country with the most distinct recordings when considering spatial correlation. Our analysis includes a comparison of musical attributes and styles that contribute to the ‘uniqueness’ of the music of each country

The TOM core complex: the general protein import pore of the outer membrane of mitochondria

Abstract: Translocation of nuclear-encoded preproteins across the outer membrane of mitochondria is mediated by the multicomponent transmembrane TOM complex. We have isolated the TOM core complex of Neurospora crassa by removing the receptors Tom70 and Tom20 from the isolated TOM holo complex by treatment with the detergent dodecyl maltoside. It consists of Tom40, Tom22, and the small Tom components, Tom6 and Tom7. This core complex was also purified directly from mitochondria after solubilization with dodecyl maltoside. The TOM core complex has the characteristics of the general insertion pore; it contains high-conductance channels and binds preprotein in a targeting sequence-dependent manner. It forms a double ring structure that, in contrast to the hole complex, lacks the third density seen in the latter particles. Three-dimensional reconstruction by electron tomography exhibits two open pores traversing the complex with a diameter of similar to 2.1 nm and a height of similar to 7 nm. Tom40 is the key structural element of the TOM core complex

Survey of large protein complexes D. vulgaris reveals great structural diversity

An unbiased survey has been made of the stable, most abundant multi-protein complexes in Desulfovibrio vulgaris Hildenborough (DvH) that are larger than Mr {approx} 400 k. The quaternary structures for 8 of the 16 complexes purified during this work were determined by single-particle reconstruction of negatively stained specimens, a success rate {approx}10 times greater than that of previous 'proteomic' screens. In addition, the subunit compositions and stoichiometries of the remaining complexes were determined by biochemical methods. Our data show that the structures of only two of these large complexes, out of the 13 in this set that have recognizable functions, can be modeled with confidence based on the structures of known homologs. These results indicate that there is significantly greater variability in the way that homologous prokaryotic macromolecular complexes are assembled than has generally been appreciated. As a consequence, we suggest that relying solely on previously determined quaternary structures for homologous proteins may not be sufficient to properly understand their role in another cell of interest

Compression-based Modelling of Musical Similarity Perception

Similarity is an important concept in music cognition research since the similarity between (parts of) musical pieces determines perception of stylistic categories and structural relationships between parts of musical works. The purpose of the present research is to develop and test models of musical similarity perception inspired by a transformational approach which conceives of similarity between two perceptual objects in terms of the complexity of the cognitive operations required to transform the representation of the first object into that of the second, a process which has been formulated in informationtheoretic terms. Specifically, computational simulations are developed based on compression distance in which a probabilistic model is trained on one piece of music and then used to predict, or compress, the notes in a second piece. The more predictable the second piece according to the model, the more efficiently it can be encoded and the greater the similarity between the two pieces. The present research extends an existing information-theoretic model of auditory expectation (IDyOM) to compute compression distances varying in symmetry and normalisation using high-level symbolic features representing aspects of pitch and rhythmic structure. Comparing these compression distances with listeners’ similarity ratings between pairs of melodies collected in three experiments demonstrates that the compression-based model provides a good fit to the data and allows the identification of representations, model parameters and compression-based metrics that best account for musical similarity perception. The compression-based model also shows comparable performance to the best-performing algorithms on the MIREX 2005 melodic similarity task

Zernike Phase Contrast Electron Microscopy with a Spherically Corrected Foil Lens

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009</jats:p

Interrogating melodic similarity:a definitive phenomenon or the product of interpretation?

The nature of melodic similarity is interrogated through a survey of the different means by which the phenomenon has been studied, examination of methods for measuring melodic similarity, a Monte Carlo analysis of data from the experiment which formed the basis for the ‘ground truth’ used in the MIREX 2005 contest on melodic similarity, and examples of interest in the music of Mozart. Melodic similarity has been studied by a number of means, sometimes quite contrasting, which lead to important differences in the light of the finding that similarity is dependent on context. Models of melodic similarity based on reduction show that the existence of multiple possible reductions forms a natural basis for similarity to depend on interpretation. Examination of the MIREX 2005 data shows wide variations in subjects’ judgements of melodic similarity and some evidence that the perceived similarity between two melodies can be influenced by the presence of a third melody. Examples from Mozart suggest that he deliberately exploited the possibilities inherent in recognising similarity through different interpretations. It is therefore proposed that similarity be thought of not as a distinct and definite function of two melodies but as something created in the minds of those who hear the melodies