Temporal Networks

A great variety of systems in nature, society and technology -- from the web of sexual contacts to the Internet, from the nervous system to power grids -- can be modeled as graphs of vertices coupled by edges. The network structure, describing how the graph is wired, helps us understand, predict and optimize the behavior of dynamical systems. In many cases, however, the edges are not continuously active. As an example, in networks of communication via email, text messages, or phone calls, edges represent sequences of instantaneous or practically instantaneous contacts. In some cases, edges are active for non-negligible periods of time: e.g., the proximity patterns of inpatients at hospitals can be represented by a graph where an edge between two individuals is on throughout the time they are at the same ward. Like network topology, the temporal structure of edge activations can affect dynamics of systems interacting through the network, from disease contagion on the network of patients to information diffusion over an e-mail network. In this review, we present the emergent field of temporal networks, and discuss methods for analyzing topological and temporal structure and models for elucidating their relation to the behavior of dynamical systems. In the light of traditional network theory, one can see this framework as moving the information of when things happen from the dynamical system on the network, to the network itself. Since fundamental properties, such as the transitivity of edges, do not necessarily hold in temporal networks, many of these methods need to be quite different from those for static networks

A Dynamic Approach to Rhythm in Language: Toward a Temporal Phonology

It is proposed that the theory of dynamical systems offers appropriate tools to model many phonological aspects of both speech production and perception. A dynamic account of speech rhythm is shown to be useful for description of both Japanese mora timing and English timing in a phrase repetition task. This orientation contrasts fundamentally with the more familiar symbolic approach to phonology, in which time is modeled only with sequentially arrayed symbols. It is proposed that an adaptive oscillator offers a useful model for perceptual entrainment (or `locking in') to the temporal patterns of speech production. This helps to explain why speech is often perceived to be more regular than experimental measurements seem to justify. Because dynamic models deal with real time, they also help us understand how languages can differ in their temporal detail---contributing to foreign accents, for example. The fact that languages differ greatly in their temporal detail suggests that these effects are not mere motor universals, but that dynamical models are intrinsic components of the phonological characterization of language.Comment: 31 pages; compressed, uuencoded Postscrip

Modeling Abnormal Priming in Alzheimer's Patients with a Free Association Network

Alzheimer's Disease irremediably alters the proficiency of word search and retrieval processes even at its early stages. Such disruption can sometimes be paradoxical in specific language tasks, for example semantic priming. Here we focus in the striking side-effect of hyperpriming in Alzheimer's Disease patients, which has been well-established in the literature for a long time. Previous studies have evidenced that modern network theory can become a powerful complementary tool to gain insight in cognitive phenomena. Here, we first show that network modeling is an appropriate approach to account for semantic priming in normal subjects. Then we turn to priming in degraded cognition: hyperpriming can be readily understood in the scope of a progressive degradation of the semantic network structure. We compare our simulation results with previous empirical observations in diseased patients finding a qualitative agreement. The network approach presented here can be used to accommodate current theories about impaired cognition, and towards a better understanding of lexical organization in healthy and diseased patients

Problem-finding as a research strategy connecting undergraduate learning with staff research in contemporary education institutions

While problem-solving is defined as a research method based on a number of givens in a linear process, problem-finding is an open-ended mode of design, actively engaging participants in a reciprocal discourse. This method of learning by doing is implicit in design education. To examine problem-solving in the context of undergraduate study a collaborative staff–student research project is presented in the form of a case study. By continuing to find ‘problems’, design educators and students alike are challenged to push the boundaries of the discipline and frame it more centrally as an agent of change in society and culture. In a development of my Ph.D. and HEA Teaching Fellowship the design process is framed as a bridge between academic research and student employability. In this context I suggest that research strategies developed through doctoral study extend and substantiate teaching and learning in design

Detection of presence, position and correct positioning of components on a PCB by image processing

Un recorrido por el funcionamiento del procesamiento de imagen y sus diferentes procesos, entrando en diferentes funcionamiento matemáticos de los mismos. Además, voy un poco más allá entrando en procesos adyacentes no imprescindibles del proceso de procesar una imagen, como puede ser el tratamiento que se hace del color o cuando se realiza un realce de una imagen durante el procesamiento de esta. Por último, se cuenta el funcionamiento de las redes neuronales, tanto como funciona matemática y lógicamente una neurona por si sola y un esquema de la misma. Añadiendo como se realizaría una red neuronal para el procesamiento de imagen en Python.Departamento de Organización de Empresas y Comercialización e Investigación de MercadosGrado en Ingeniería en Electrónica Industrial y Automátic

Anatomy of the sleep-wake systems in four species of Equid

A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Medicine. Johannesburg, 2017Within the order Perissodactyla the physiological measurable parameters of sleep have been investigated in a number of species, however no studies exist that describe the neuronal organisation and morphology of the sleep-wake systems in any of its members. The central aim of this dissertation is to address this gap by providing the first complete description of the somnogenic systems in the basal forebrain, diencephalon, midbrain and pons of four equid species; the donkey, horse, plains and mountain zebra. By means of standard immunohistochemical techniques the cholinergic, catecholaminergic, serotonergic, orexinergic and GABAergic systems were identified and qualitatively described in each of the four species. The results revealed that, for the most part, the nuclear organisation and morphology of the sleepwake systems did not differ between the species examined, and displayed the typical mammalian organisational plan. However, two novel findings were noted: 1) the presence of tyrosine hydroxylase neurons in the predominantly GABAergic thalamic reticular nucleus; 2) the presence of a medial cluster of parvocellular orexinergic neurons within the hypothalamus. It is proposed that the population of tyrosine hydroxylase neurons in the thalamic reticular nucleus likely play a role in postural maintenance during standing rapid eye movement sleep and potentially contribute to memory consolidation in mammals with short sleep times. Additionally, the parvocellular cluster of orexin neurons is hypothesised to balance short sleep time and appetite drive in larger animals with high-energy demands and a low trophic status. The data produced from this dissertation extends the pre-existing phylogenetic database and offers further opportunity for reliable comparisons across mammals towards a more complete definition of the phenomenon of sleep.LG201