214 research outputs found
Stiff knots
We report on the geometry and mechanics of knotted stiff strings. We discuss
both closed and open knots. Our two main results are: (i) Their equilibrium
energy as well as the equilibrium tension for open knots depend on the type of
knot as the square of the bridge number; (ii) Braid localization is found to be
a general feature of stiff strings entanglements, while angles and knot
localization are forbidden. Moreover, we identify a family of knots for which
the equilibrium shape is a circular braid. Two other equilibrium shapes are
found from Monte Carlo simulations. These three shapes are confirmed by
rudimentary experiments. Our approach is also extended to the problem of the
minimization of the length of a knotted string with a maximum allowed
curvature.Comment: Submitted to Phys. Rev.
Towards a Statistical Physics of Human Mobility
In this paper, we extend some ideas of statistical physics to describe the
properties of human mobility. From a physical point of view, we consider the
statistical empirical laws of private cars mobility, taking advantage of a GPS
database which contains a sampling of the individual trajectories of 2% of the
whole vehicle population in an Italian region. Our aim is to discover possible
"universal laws" that can be related to the dynamical cognitive features of
individuals. Analyzing the empirical trip length distribution we study if the
travel time can be used as universal cost function in a mesoscopic model of
mobility. We discuss the implications of the elapsed times distribution between
successive trips that shows an underlying Benford's law, and we study the rank
distribution of the average visitation frequency to understand how people
organize their daily agenda. We also propose simple stochastic models to
suggest possible explanations of the empirical observations and we compare our
results with analogous results on statistical properties of human mobility
presented in the literature
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ELSA Italy
In the last 50 years, Italy has experienced a relevant transformation, starting from an emigrant nation (according to the last statistics from the Ministry of the Interior, there are more than 4.636.647 Italians still living abroad) to become an immigrant destination.
From 1970 until now, migrant citizens with regular residence permits in Italy have increased, with a rate of growth that looks almost unstoppable: at the beginning of 2017, there were more than 5,047,028 foreign nationals resident in Italy.
This numbers, added to the illegal immigrants whose numbers are difficult to define, outline a complex situation, characterized by immigrant flows from almost 200 different countries, especially Central Eastern Europe (Albania, Romania and Ukraine), Northern Africa (Morocco), China and the Indian subcontinent (Pakistan, India, and Sri Lanka).
This historically important phenomenon requires in-depth analysis in order to evaluate the effectiveness of the Italian legislation and intervention policies, and to find concrete solutions to help immigrants settling in our country
The tsunamigenic potential of landslide-generated tsunamis on the Vavilov seamount
The investigation of submarine volcanoes and the tsunamigenic potential of possible movements on their flanks is arduous. In most cases, the lack of specific information about the eruptionsâ history and their consequences does not allow a comprehensive analysis in terms of hazard. Nevertheless, useful clues on the possible occurrence of mass movements on seamounts can be obtained from a series of research fields. These account for morphological studies, observations of hydrothermal activity, collection of geophysical data (for example, detailed DEM, seismic profiles, magnetic data), etc. In this context, this study presents new bathymetric data of the Vavilov submarine volcano (Tyrrhenian Sea, Italy) and a detailed morphological analysis of the structure. The latter allows the identification of zones potentially prone to mass movements and the development of numerical scenarios to investigate the tsunami potential associated to these movements on the Vavilov flanks. Results prove that the waves generated by the mass displacements in the proposed scenarios (involving sliding volumes between 0.32 km3 and 1.7 km3) reach maximum values in the order of centimetres, not considering dispersive effects. Eventually, a scenario involving the partial collapse of the west flank of the Vavilov Seamount is simulated, although the occurrence of such an event in the past is still debated due to the uncertainties related to the origin and development of the volcano dome. In this scenario, water elevation as high as 10 m are found in large portions of the Tyrrhenian coasts: waves are large enough to emplace sizeable tsunami deposits onshore, that could have been preserved until today in some specific stretches of the coast and could be detected by a finalised geological search. This study belongs to a series of works devoted to the submarine structures of the Tyrrhenian Sea aiming to disclose the tsunamigenic potential of submarine mass movements on their flanks
Idiopathic pulmonary fibrosis telemedicine management during COVID-19 outbreak
The present report investigates the impact of a Telemedicine Service (TMS) on the management of Idiopathic Pulmonary Fibrosis (IPF) during coronavirus disease of 2019 (COVID-19) outbreak in Italy. The TMS comprised 3 phone numbers, active 12 h per day, and an email address, monitored every 4 h by trained physicians; chat-and videoconference-services were also offered. At the end of the study period, our staff contacted all patients, to get information about the final outcome (i.e. composite hospitalisations/all causes of death). Outcomes were compared with a cohort of patients who attended our unit in the same period of the previous year (when no TMS was available). 189 patients participated in the present study. From 11th March to 4th May 2020, 61% of patients made at least one TMS access, mostly by emails (53%), followed by phone calls (33%). With regard to the primary outcome, TMS patients experienced a significant lower rate of events of the 182 patients of the no-TMS cohort (p < 0.001). Specifically, a significant difference was observed for IPF hospitalisation (p < 0.001) whereas no differences were observed with regard to deaths (p = 0.64). TMS permits patients to be followed up even during COVID-19 lockdown, with an encouraging impact on outcomes
Evaluation of tsunamigenic hazard through numerical modeling from seismic and non-seismic sources in the Crotone offshore (Calabria, Southern Italy)
Tsunamis in the Mediterranean Sea can be considered among the major sources of hazard, both for the extension of the area that can be involved by the water impact and for the closeness of potential sources to the coast, which reduces dramatically the alert and evacuation time. Moreover, landslides, as other non-seismic tsunami sources, are often characterized by a lack of precursors (such as seismic shaking), a reason for which the ensuing waves are sometimes called âsurprise tsunamisâ
Multi-scale spatio-temporal analysis of human mobility
The recent availability of digital traces generated by phone calls and online logins has significantly increased the scientific understanding of human mobility. Until now, however, limited data resolution and coverage have hindered a coherent description of human displacements across different spatial and temporal scales. Here, we characterise mobility behaviour across several orders of magnitude by analysing âŒ850 individuals' digital traces sampled every âŒ16 seconds for 25 months with âŒ10 meters spatial resolution. We show that the distributions of distances and waiting times between consecutive locations are best described by log-normal and gamma distributions, respectively, and that natural time-scales emerge from the regularity of human mobility. We point out that log-normal distributions also characterise the patterns of discovery of new places, implying that they are not a simple consequence of the routine of modern life
The physics of spreading processes in multilayer networks
The study of networks plays a crucial role in investigating the structure,
dynamics, and function of a wide variety of complex systems in myriad
disciplines. Despite the success of traditional network analysis, standard
networks provide a limited representation of complex systems, which often
include different types of relationships (i.e., "multiplexity") among their
constituent components and/or multiple interacting subsystems. Such structural
complexity has a significant effect on both dynamics and function. Throwing
away or aggregating available structural information can generate misleading
results and be a major obstacle towards attempts to understand complex systems.
The recent "multilayer" approach for modeling networked systems explicitly
allows the incorporation of multiplexity and other features of realistic
systems. On one hand, it allows one to couple different structural
relationships by encoding them in a convenient mathematical object. On the
other hand, it also allows one to couple different dynamical processes on top
of such interconnected structures. The resulting framework plays a crucial role
in helping achieve a thorough, accurate understanding of complex systems. The
study of multilayer networks has also revealed new physical phenomena that
remain hidden when using ordinary graphs, the traditional network
representation. Here we survey progress towards attaining a deeper
understanding of spreading processes on multilayer networks, and we highlight
some of the physical phenomena related to spreading processes that emerge from
multilayer structure.Comment: 25 pages, 4 figure
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