On the formation of structure in growing networks

Based on the formation of triad junctions, the proposed mechanism generates networks that exhibit extended rather than single power law behavior. Triad formation guarantees strong neighborhood clustering and community-level characteristics as the network size grows to infinity. The asymptotic behavior is of interest in the study of directed networks in which (i) the formation of links cannot be described according to the principle of preferential attachment; (ii) the in-degree distribution fits a power law for nodes with a high degree and an exponential form otherwise; (iii) clustering properties emerge at multiple scales and depend on both the number of links that newly added nodes establish and the probability of forming triads; and (iv) groups of nodes form modules that feature less links to the rest of the nodes.Comment: 17 pages, 9 figures, we apply the proposed mechanism to generate network realizations that resemble the degree distribution and clustering properties of an empirical network with no directed cycles (i.e., when the model parameter n=0), updated reference

Using Bursty Announcements for Detecting BGP Routing Anomalies

Despite the robust structure of the Internet, it is still susceptible to disruptive routing updates that prevent network traffic from reaching its destination. Our research shows that BGP announcements that are associated with disruptive updates tend to occur in groups of relatively high frequency, followed by periods of infrequent activity. We hypothesize that we may use these bursty characteristics to detect anomalous routing incidents. In this work, we use manually verified ground truth metadata and volume of announcements as a baseline measure, and propose a burstiness measure that detects prior anomalous incidents with high recall and better precision than the volume baseline. We quantify the burstiness of inter-arrival times around the date and times of four large-scale incidents: the Indosat hijacking event in April 2014, the Telecom Malaysia leak in June 2015, the Bharti Airtel Ltd. hijack in November 2015, and the MainOne leak in November 2018; and three smaller scale incidents that led to traffic interception: the Belarusian traffic direction in February 2013, the Icelandic traffic direction in July 2013, and the Russian telecom that hijacked financial services in April 2017. Our method leverages the burstiness of disruptive update messages to detect these incidents. We describe limitations, open challenges, and how this method can be used for routing anomaly detection.Comment: 16 pages, 13 figures, 4 tabl

IMPACT OF INGREDIENTS AND PROCESSING TECHNOLOGIES ON STRUCTURAL AND NUTRITIONAL PROPERTIES OF REDUCED-FAT FOODS

In the last decades, the demand for nutritionally-improved food has raised, drawing the attention of researchers on new solutions for product development. The design of foods able to satisfy specific sensory and nutritional functionalities requires a better understanding of the relationships between the composition of food materials, the effects of processing on their quality characteristics and structure, and their behavior during digestion. This PhD thesis aimed at evaluating how ingredients and technology affect structural properties of different reduced-fat matrices. Biscuits and whipping cream were used as case studies with different specific aims concerning the effects of ingredients and/or production technology. In particular, resistant starch, raw and extruded bean flour were evaluated as structuring ingredients in reduced fat biscuits, in combination with polydextrose or double emulsion as fat replacers. The effect on structural, nutritional and sensory properties of final biscuits were investigated. For whipping cream, gelatin addition and homogenization condition effects on structure and stability were evaluated, both immediately after production and after three weeks of storage. Design of Experiments techniques coupled with Response Surface Methodology were used for the multivariate investigation of both formulation and processing effect. Results from the biscuit case study demonstrated that combination of polydextrose and resistant starch allowed to obtain a reduced-fat biscuit (- 44 % fat) with structural characteristics similar to those of a standard full-fat biscuit prepared with shortening or butter. The use of extruded bean flour allowed to obtain biscuits nearly comparable to a traditional reduced-fat product, but with improved nutritional profile. The presented data suggest a hypoglycaemic potential of bean-enriched biscuits, to be confirmed by a dedicated in vivo study. Desirable nutritional value of bean powders, including high protein content and slow starch digestibility, may be successfully exploited in biscuits. On the other hand, the study of double emulsions by D-optimal design allowed to improve the knowledge about the effect of internal water gelling and the proportion of water and oil in the emulsion on yield, rheological behaviour and stability. However, the use of double emulsion in reduced-fat biscuits requires further investigations, in order to understand how to improve emulsion structuring and its effect on dough properties. Results from the whipping cream case-study demonstrated that the combination of gelatin addition and high homogenization pressure may be successfully exploited for the development of reduced-fat whipping cream (25 g/100g fat), with good quality characteristics and stability. D-optimal design and Response Surface Methodology resulted to be effective tools for the study of cream processing at a pilot level, allowing the collection of high quality information on the effect of the studied factors and their interactions, with a limited experimental effort. In particular, gelatin addition at a concentration of 0.25 g/100g, in combination with k-carrageenan, increased initial consistency of cream samples, leading to final overrun values even improved with respect to those obtained for commercial samples, without affecting texture properties and stability. Depending on gelatin concentration, homogenization pressure revealed a great potential to modulate whipping properties. The multidisciplinary approach adopted, comprehensive of all the functionality aspects related to a food product, may represent a starting point for the design of foods with targeted quality features and behavior during consumption. In such a complex investigation field, Experimental Design techniques coupled with multivariate analyses of the experimental data have confirmed to be effective tools for the characterization and optimization of both food formulation and processing. The developed mathematical models can be applied for reverse engineering and quality-by-design approaches, thus benefit both researchers and companies

Power-law weighted networks from local attachments

This letter introduces a mechanism for constructing, through a process of distributed decision-making, substrates for the study of collective dynamics on extended power-law weighted networks with both a desired scaling exponent and a fixed clustering coefficient. The analytical results show that the connectivity distribution converges to the scaling behavior often found in social and engineering systems. To illustrate the approach of the proposed framework we generate network substrates that resemble steady state properties of the empirical citation distributions of (i) publications indexed by the Institute for Scientific Information from 1981 to 1997; (ii) patents granted by the U.S. Patent and Trademark Office from 1975 to 1999; and (iii) opinions written by the Supreme Court and the cases they cite from 1754 to 2002.Comment: 18 pages, 3 figures; Proceedings of the IEEE Conference on Decision and Control and the European Control Conference, Orlando, FL, Dec. 2011; Added references; We modified the model in order to take into account extended power-law distributions which better fit to the citations data sets; Added proofs of theorems; Shorten version; Updated plo

Contributions to the multi-frequency control of gridtied voltage source converters

El interés por la producción de energía limpia está en aumento y la generación de este tipo de energía se puede fomentar mediante la instalación de generadores locales. Dichos generadores son conectados a la red de distribución a través de convertidores de potencia. Al mismo tiempo el número de cargas conectadas a la red está incrementando y con ello el número de cargas no lineales. Estas últimas consumen corrientes armónicas y esto provoca distorsión armónica a la red. En esta tesis se estudia y se presentan contribuciones en el control de los convertidores de potencia para que al mismo tiempo que se inyecta potencia, el convertidor sea capaz de actuar adecuadamente frente a la distorsión armónica del voltaje de la red (control multifrecuencial). En primer lugar, esta tesis cubrirá el estudio de las diferentes técnicas de control de corrientes armónicas y también de las diferentes técnicas de sincronización y detección de componentes armónicas de tensión presentes en la red. En cuanto al cálculo de referencias de corrientes armónicas, se explican las principales variantes dependiendo de la funcionalidad deseada y se estudia la entrega de potencia instantánea constante incluso con red distorsionada. Además, se propone un nuevo método de cálculo para eliminar las principales oscilaciones de potencia sin exceder las limitaciones de distorsión de corrientes. También se describen las limitaciones del convertidor cuando se trabaja con componentes fundamentales y armónicas. Se analizan los principales saturadores multifrecuenciales para evitar la sobremodulación y se propone un nuevo saturador que no empeora la dinámica total del sistema y siempre consigue el mínimo THD de corriente. Por último, se aborda la problemática de la distorsión armónica del voltaje de red. Primero se estudia la compensación de las corrientes consumidas por cargas locales y después se propone la compensación directa de la tensión del PCC. En esta tesis se intenta incrementar el número de funcionalidades que puede desempeñar el convertidor para que además de entregar potencia, sea capaz de mejorar la calidad de la red, sin exceder las limitaciones físicas del convertidor. Cada una de las contribuciones es validada mediante resultados de simulación y experimentales

Modern human changes in regulatory regions implicated in cortical development

Background: Recent paleogenomic studies have highlighted a very small set of proteins carrying modern human-specific missense changes in comparison to our closest extinct relatives. Despite being frequently alluded to as highly relevant, species-specific differences in regulatory regions remain understudied. Here, we integrate data from paleogenomics, chromatin modification and physical interaction, and single-cell gene expression of neural progenitor cells to identify derived regulatory changes in the modern human lineage in comparison to Neanderthals/Denisovans. We report a set of genes whose enhancers and/or promoters harbor modern human single nucleotide changes and are active at early stages of cortical development. Results: We identified 212 genes controlled by regulatory regions harboring modern human changes where Neanderthals/Denisovans carry the ancestral allele. These regulatory regions significantly overlap with putative modern human positively-selected regions and schizophrenia-related genetic loci. Among the 212 genes, we identified a substantial proportion of genes related to transcriptional regulation and, specifically, an enrichment for the SETD1A histone methyltransferase complex, known to regulate WNT signaling for the generation and proliferation of intermediate progenitor cells. Conclusions: This study complements previous research focused on protein-coding changes distinguishing our species from Neanderthals/Denisovans and highlights chromatin regulation as a functional category so far overlooked in modern human evolution studies. We present a set of candidates that will help to illuminate the investigation of modern human-specific ontogenetic trajectories

Procesos biocatalíticos para la producción de carbohidratos bioactivos: fructooligosacáridos y quitooligosacáridos

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 14-07-2017Esta tesis tiene embargado el acceso al texto completo hasta el 14-01-201

Anatomical pathways for auditory memory II: information from rostral superior temporal gyrus to dorsolateral temporal pole and medial temporal cortex

Auditory recognition memory in non-human primates differs from recognition memory in other sensory systems. Monkeys learn the rule for visual and tactile delayed matching-to-sample within a few sessions, and then show one-trial recognition memory lasting 10–20 min. In contrast, monkeys require hundreds of sessions to master the rule for auditory recognition, and then show retention lasting no longer than 30–40 s. Moreover, unlike the severe effects of rhinal lesions on visual memory, such lesions have no effect on the monkeys' auditory memory performance. The anatomical pathways for auditory memory may differ from those in vision. Long-term visual recognition memory requires anatomical connections from the visual association area TE with areas 35 and 36 of the perirhinal cortex (PRC). We examined whether there is a similar anatomical route for auditory processing, or that poor auditory recognition memory may reflect the lack of such a pathway. Our hypothesis is that an auditory pathway for recognition memory originates in the higher order processing areas of the rostral superior temporal gyrus (rSTG), and then connects via the dorsolateral temporal pole to access the rhinal cortex of the medial temporal lobe. To test this, we placed retrograde (3% FB and 2% DY) and anterograde (10% BDA 10,000 mW) tracer injections in rSTG and the dorsolateral area 38DL of the temporal pole. Results showed that area 38DL receives dense projections from auditory association areas Ts1, TAa, TPO of the rSTG, from the rostral parabelt and, to a lesser extent, from areas Ts2-3 and PGa. In turn, area 38DL projects densely to area 35 of PRC, entorhinal cortex (EC), and to areas TH/TF of the posterior parahippocampal cortex. Significantly, this projection avoids most of area 36r/c of PRC. This anatomical arrangement may contribute to our understanding of the poor auditory memory of rhesus monkeys

VIE Project: Cultural values and socioeconomic factors as determinants of entrepreneurial intentions

This paper describes a research project currently being developed by the authors. It aims to analyse the role played by psychosocial, cultural and socioeconomic factors in shaping the entrepreneurial intention. Survey methods will be used on a population of potential entrepreneurs (having not yet performed actual entrepreneurial behaviours). In this sense, undergraduate students and individuals contacting business support centres will be considered as part of the sample. We expect to get a clearer understanding of the psychosocial elements, socioeconomic factors and cultural values affecting the venture-creation decision. The results would be important to policy makers (showing them what to encourage), to practitioners (what to do better), and to researchers (what to clarify)