Speaker
Daniele Quercia

Description For the last year or so, we have been working on studying social media in the context of London. By combining what Twitter users in a variety of London neighborhoods talk about with census data, we showed that certain topics are correlated (positively and negatively) with neighborhood deprivation. Users in more deprived neighborhoods tweet about wedding parties, matters expressed in Spanish/Portuguese, and celebrity gossips. By contrast, those in less deprived neighborhoods tweet about vacations, professional use of social media, environmental issues, sports, and health issues. More recently, we launched two crowdsourcing websites. First, we launched urbanopticon.org, which extracts Londoners' mental images of the city. By testing which places are remarkable and unmistakable and which places represent faceless sprawl, we are able to draw the recognizability map of London [1,2]. The site has attracted tens of thousands of players, and I will show you the results published in WWW this year. The second site is called urbangems.org. This crowdsources visual perceptions of quiet, beauty and happiness across the city using Google Street View pictures. The aim is to identify the visual cues that are generally associated with concepts difficult to define such beauty, happiness, quietness, or even deprivation [3,4]. The site has been awarded the A.T. Kearney Prize and has been featured in falling-walls.com 2012 in Berlin. [1] Look familiar? http://bit.ly/HgvqZ7 [2] Psychological Maps 2.0: A web engagement enterprise starting in London. WWW 2013 http://bit.ly/189AzfL [3] Project aims to crowdsource what makes a happy city http://bbc.in/15WMnI9 [4] Aesthetic Capital: What Makes London Look Beautiful, Quiet, and Happy? CSCW 2014 http://bit.ly/19NTEr6

Speaker
Martin Haro

Description In the last few years some Music Information Retrieval (MIR) researchers have spotted important drawbacks in applying standard successful-inmonophonic algorithms to polyphonic music classification and similarity assessment. Noticeably, these so called “Bag-of-Frames” (BoF) algorithms share a common set of assumptions. These assumptions are substantiated in the belief that the numerical descriptions extracted from short-time audio excerpts (or frames) are enough to capture relevant information for the task at hand, that these frame-based audio descriptors are time independent, and that descriptor frames are well described by Gaussian statistics. Thus, if we want to improve current BoF algorithms we could: i) improve current audio descriptors, ii) include temporal information within algorithms working with polyphonic music, and iii) study and characterize the real statistical properties of these frame-based audio descriptors. From a literature review, we have detected that many works focus on the first two improvements, but surprisingly, there is a lack of research in the third one. Therefore, in this thesis we analyze and characterize the statistical distribution of common audio descriptors of timbre, tonal and loudness information. Contrary to what is usually assumed, our work shows that the studied descriptors are heavy-tailed distributed and thus, they do not belong to a Gaussian universe. This new knowledge led us to propose new algorithms that show improvements over the BoF approach in current MIR tasks such as genre classification, instrument detection, and automatic tagging of music. Furthermore, we also address new MIR tasks such as measuring the temporal evolution of Western popular music. Finally, we highlight some promising paths for future audio-content MIR research that will inhabit a heavy-tailed universe.

Speaker
Susanna Manrubia

Description The relationship between genotype and phenotype is many-to-many. In particular, genotypes encoding a particular phenotype form vast, connected networks that often span the whole space of possible genotypes. Regarding their topological properties, genotype networks are highly heterogeneous in degree and, in most know cases, assortative (as in RNA and proteins). These properties have important effects on the dynamics of populations evolving on genotype networks. As time elapses, the probability that a random walker on such networks visits nodes of increasingly higher degree augments. In evolutionary terms, this implies that the probability that a population changes phenotype depends in a non-trivial way on the time the population has maintained the current one. We derive a mathematical framework that quantifies this phenotypic entrapment and explicitly shows the dependence on measurable quantities such as network assortativity, mutation rate, or fitness of the phenotype. These results have important implications in a reliable definition of a molecular clock, which in general has a non-constant ticking rate due to the heterogeneity of genotype networks.

Speaker
Rubén Requejo

Description In this talk I will present a simple model of evolution of cooperation (neutral individuals) and defection (parasitism) in which the existence of limiting resources triggers a self-organized state out of equilibrium where both behaviours coexist. Such steady state is stable out of the equilibrium in a thermodynamic sense, as there is a constant influx and outflux of resources into and out of the system. The stylished model allows for an intuitive explanation on how ecosystems and monetary systems self-organize to maintain behavioural diversity, and presents an example in which the competitive exclusion principle fails. The results also show that the discovery of new resource sources promotes parasitic behaviours during the time of population growth, which may give some insights to why corruption seems to spread whenever wealth increases happen in a short time span.

Speaker
Oscar N. Mesquita

Description 1) In the first part of the talk, I will present our results on single-molecule DNA stretching experiments using Optical Tweezers. From the experiments we obtain the persistence and contour lengths of the DNA molecule. When DNA interacts with cationic cyclodextrin (CD), the persistence length of the complex formed changes non-monotonically: for smaller concentrations of CD the persistence length decreases and then increases as the CD concentration increases further. We propose a two-site quenched disorder statistical model, which fits the data very well and returns the local changes in persistence length, chemical affinity and cooperativity of DNA-CD reaction. Our model also fits well the literature data for the HU-DNA interaction. 2) In the second part of the talk, I will present “Defocusing Microscopy”, a simple bright-field optical microscopy technique developed by us, which allows actual 3D imaging of transparent objects (phase objects). I will show our results for red blood cells (RBC) both for isotonic and hypotonic concentrations, where the image of the lower RBC membrane deformed due to adhesion to the glass substrate, can clearly be distinguished from the image of the upper membrane. In addition, by studying contrast fluctuations of the images we can obtain the elastic constants along each RBC membrane.