A numerical investigation of the jamming transition in traffic flow on diluted planar networks

In order to develop a toy model for car's traffic in cities, in this paper we analyze, by means of numerical simulations, the transition among fluid regimes and a congested jammed phase of the flow of "kinetically constrained" hard spheres in planar random networks similar to urban roads. In order to explore as timescales as possible, at a microscopic level we implement an event driven dynamics as the infinite time limit of a class of already existing model (e.g. "Follow the Leader") on an Erdos-Renyi two dimensional graph, the crossroads being accounted by standard Kirchoff density conservations. We define a dynamical order parameter as the ratio among the moving spheres versus the total number and by varying two control parameters (density of the spheres and coordination number of the network) we study the phase transition. At a mesoscopic level it respects an, again suitable adapted, version of the Lighthill-Whitham model, which belongs to the fluid-dynamical approach to the problem. At a macroscopic level the model seems to display a continuous transition from a fluid phase to a jammed phase when varying the density of the spheres (the amount of cars in a city-like scenario) and a discontinuous jump when varying the connectivity of the underlying network.Comment: accepted in Int.J.Mod.Phys.

New technologies and the right to freedom of peaceful assembly and association

Defence date: 30 April 2020 (Online)Examining Board: Professor Martin Scheinin (EUI; Supervisor), Professor Gàbor Halmai (EUI), Professor Sarah H. Cleveland (University of Columbia), Dr Michael Hamilton (University of East Anglia)The thesis analyses the international human rights law framework on the exercise of the freedom of peaceful assembly and the freedom of association at a universal and regional European level, to assess whether the current international law regime covers the exercise of these two rights in the online context and with the use of new technologies. While applying the current framework to the online exercise of these rights, the thesis identifies those areas where international human rights law would require adaptation in order to ensure the respect, protection and fulfillment of these important political rights. The thesis provides examples of how people organize and collectively express themselves online, that is assemble and associate, with a particular focus on political parties. The areas identified and analysed in the thesis can generally be summarized as; the need to re-assess the core, and thus, the definition of these two rights in their online manifestation; the nature of the Internet and social media as a new space on which these fundamental rights are exercised; the private enforcement of fundamental rights by Internet intermediaries and the responsibility of the State in this regard; the limitations already placed over the exercise of assembly and association online, such as the use of algorithms, take-down and regulation of content; State restrictions already placed over the exercise of these rights online such as filtering and shut-down of the Internet; and the potential evolution of a new ‘right to the Internet’. The thesis proposes that the human rights framework contains the resilience and flexibility to face this changing environment for the exercise of rights and with the requisite adjustments, can serve to protect the exercise these fundamental political rights online

Elections in digital times: a guide for electoral practitioners

Strengthening democracy and electoral processes in the era of social media and Artificial Intelligence Democracy requires free, periodic, transparent, and inclusive elections. Freedom of expression, freedom of the press, and the right to political participation are also critical to societies ruled by the respect of human rights. In today’s rapidly evolving digital environment, opportunities for communication between citizens, politicians and political parties are unprecedented –– with information related to elections flowing faster and easier than ever, coupled with expanded opportunities for its verification and correction by a growing number of stakeholders. However, with billions of human beings connected, and disinformation and misinformation circulating unhinged around the networks, democratic processes and access to reliable information are at risk. With an estimated 56.8% of the world’s population active on social media and an estimate of 4 billion eligible voters, the ubiquity of social networks and the impact of Artificial Intelligence can intentionally or unintentionally undermine electoral processes, thereby delegitimizing democracies worldwide. In this context, all actors involved in electoral processes have an essential role to play. Electoral management bodies, electoral practitioners, the media, voters, political parties, and civil society organizations must understand the scope and impact of social media and Artificial Intelligence in the electoral cycle. They also need to have access to the tools to identify who instigates and spreads disinformation and misinformation, and the tools and strategies to combat it. This handbook aims to be a toolbox that helps better understand the current scenario and share experiences of good practices in different electoral settings and equip electoral practitioners and other key actors from all over the world to ensure the credibility of the democratic system in times of profound transformations

Hyperspherical partial wave calculation for double photoionization of the helium atom at 20 eV excess energy

Hyperspherical partial wave approach has been applied here in the study of double photoionization of the helium atom for equal energy sharing geometry at 20 eV excess energy. Calculations have been done both in length and velocity gauges and are found to agree with each other, with the CCC results and with experiments and exhibit some advantages of the corresponding three particle wave function over other wave functions in use.Comment: 11 pages, 1 figure, submitted to J. Phys B: At. Mol. Opt. Phys; v2 - revised considerably, rewritten using ioplatex clas

Microtubules Regulate Local Ca2+ Spiking in Secretory Epithelial Cells

The role of the cytoskeleton in regulating Ca2+ release has been explored in epithelial cells. Trains of local Ca2+ spikes were elicited in pancreatic acinar cells by infusion of inositol trisphosphate through a whole cell patch pipette, and the Ca2+-dependent Cl- current spikes were recorded. The spikes were only transiently inhibited by cytochalasin B, an agent that acts on microfilaments. In contrast, nocodazole (5-100 µM), an agent that disrupts the microtubular network, dose-dependently reduced spike frequency and decreased spike amplitude leading to total blockade of the response. Consistent with an effect of microtubular disruption, colchicine also inhibited spiking but neither Me2SO nor beta -lumicolchicine, an inactive analogue of colchicine, had any effect. The microtubule-stabilizing agent, taxol, also inhibited spiking. The nocodazole effects were not due to complete loss of function of the Ca2+ signaling apparatus, because supramaximal carbachol concentrations were still able to mobilize a Ca2+ response. Finally, as visualized by 2-photon excitation microscopy of ER-Tracker, nocodazole promoted a loss of the endoplasmic reticulum in the secretory pole region. We conclude that microtubules specifically maintain localized Ca2+ spikes at least in part because of the local positioning of the endoplasmic reticulum

Tight junctions and the modulation of barrier function in disease

Tight junctions create a paracellular barrier in epithelial and endothelial cells protecting them from the external environment. Two different classes of integral membrane proteins constitute the tight junction strands in epithelial cells and endothelial cells, occludin and members of the claudin protein family. In addition, cytoplasmic scaffolding molecules associated with these junctions regulate diverse physiological processes like proliferation, cell polarity and regulated diffusion. In many diseases, disruption of this regulated barrier occurs. This review will briefly describe the molecular composition of the tight junctions and then present evidence of the link between tight junction dysfunction and disease

Prostaglandin- and theophylline-induced Cl secretion in rat distal colon is inhibited by microtubule inhibitors

The aim of the present study was to examine the possible role of microtubules in chloride secretion by distal rat colon stimulated by prostaglandin (PGE 2 ) and theophylline. Distal colonic tissue from male rats was mounted in Ussing chambers, and short-circuit current (I sc ) was measured to assess chloride secretion. Three microtubule inhibitors, colchicine, nocodazole, and taxol, all inhibited the stimulated I sc and reduced the 60-min integrated secretory response to PGE 2 and theophylline (▪I sc dt) by 39–52%, whereas the inactive colchicine analog lumicolchicine did not. Atropine and tetrodotoxin had no effect on stimulated chloride secretion. To confirm the source of I sc , unidirectional 22 Na + and 36 Cl − fluxes were measured in tissues exposed to lumicolchicine (control) or colchicine. Control tissues absorbed both chloride [5.0 (1.1–8.6) (median and 95% confidence interval) μeq/cm 2 /hr] and sodium [2.8 (0.9–7.2) μeq/cm 2 /hr], and this net absorption was reduced by 96% and 79%, respectively, by treatment with PGE 2 and theophylline due to an increase in serosal-to-mucosal chloride and sodium movement. Colchicine-treated tissues exhibited similar net basal chloride and sodium absorption that was reduced by 71% and 75%, respectively, by treatment with PGE 2 and theophylline. Thus the PGE 2 - and theophylline-induced increase in chloride secretion was significantly reduced by colchicine ( P <0.05 by Wilcoxon rank-sum test), whereas colchicine had no effect on PGE 2 - and theophylline-induced changes in sodium fluxes. Furthermore, the colchinine-related changes in stimulated chloride secretion were numerically similar to colchicine-related changes in stimulated I sc . These findings indicate that microtubules are required for normal PGE 2 - and theophylline-induced chloride secretion in distal rat colon and suggest that induced chloride secretion may involve vesicular insertion of ion transporters into the plasma membrane or other microtubule-dependent regulatory processes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44414/1/10620_2005_Article_BF01299864.pd