Power laws of natural swarms are fingerprints of an extended critical region

Collective biological systems display power laws for macroscopic quantities and are fertile probing grounds for statistical physics. Besides power laws, natural insect swarms present strong scale-free correlations, suggesting closeness to phase transitions. Swarms exhibit $imperfect$ dynamic scaling: their dynamical correlation functions collapse into single curves when written as functions of the scaled time $t\xi^{-z}$ ($\xi$: correlation length, $z$: dynamic exponent), but only for short times. Triggered by markers, natural swarms are not invariant under space translations. Measured static and dynamic critical exponents differ from those of equilibrium and many nonequilibrium phase transitions. Here, we show that the recently discovered scale-free-chaos phase transition of the harmonically confined Vicsek model has a novel extended critical region for finitely many insects. Unlike results of other theoretical approaches, our numerical simulations of the critical region reproduce the previously described features of natural swarms and yield static and dynamic critical exponents that agree with observations.Comment: 6 pages, 4 figures in the main text, 5 pages, 8 figures in supplementary materia

Deterministic ratchet from stationary light fields

Ratchets are dynamic systems where particle transport is induced by zero-average forces due to the interplay between nonlinearity and asymmetry. Generally, they rely on the effect of a strong external driving. We show that stationary optical lattices can be designed to generate particle flow in one direction while requiring neither noise nor driving. Such optical fields must be arranged to yield a combination of conservative (dipole) and nonconservative (radiation pressure) forces. Under strong friction all paths converge to a discrete set of limit periodic trajectories flowing in the same direction.Comment: 6 pages, 4 figure

Mean field theory of chaotic insect swarms

The harmonically confined Vicsek model displays qualitative and quantitative features observed in natural insect swarms. It exhibits a scale-free transition between single and multicluster chaotic phases. Finite-size scaling indicates that this unusual phase transition occurs at zero confinement [Phys. Rev. E 107, 014209 (2023)]. While the evidence of the scale-free-chaos phase transition comes from numerical simulations, here we present its mean-field theory. Analytically determined critical exponents are those of the Landau theory of equilibrium phase transitions plus dynamical critical exponent z = 1 and a new critical exponent φ = 0.5 for the largest Lyapunov exponent. The phase transition occurs at zero confinement and noise in the mean-field theory. The noise line of zero largest Lyapunov exponents informs observed behavior: (i) the qualitative shape of the swarm (on average, the center of mass rotates slowly at the rate marked by the winding number and its trajectory fills compactly the space, similarly to the observed condensed nucleus surrounded by vapor) and (ii) the critical exponents resemble those observed in natural swarms. Our predictions include power laws for the frequency of the maximal spectral amplitude and the winding number.This work has been supported by the FEDER/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación Grants No. PID2020-112796RB-C21 ( R.G.-A.) and No. PID2020-112796RB-C22 (L.L.B.), by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with UC3M in the line of Excellence of University Professors (EPUC3M23), and in the context of the V PRICIT (Regional Programme of Research and Technological Innovation). R.G.-A. acknowledges support from the Ministerio de Economía y Competitividad of Spain through the Formación de Doctores program Grant No. PRE2018-083807 cofinanced by the European Social Fund

Scale free chaos in the confined Vicsek flocking model

The Vicsek model encompasses the paradigm of active dry matter. Motivated by collective behavior of insects in swarms, we have studied finite size effects and criticality in the three dimensional, harmonically confined Vicsek model. We have discovered a phase transition that exists for appropriate noise and small confinement strength. On the critical line of confinement versus noise, swarms are in a state of scale-free chaos characterized by minimal correlation time, correlation length proportional to swarm size and topological data analysis. The critical line separates dispersed single clusters from confined multicluster swarms. Scale-free chaotic swarms occupy a compact region of space and comprise a recognizable `condensed' nucleus and particles leaving and entering it. Susceptibility, correlation length, dynamic correlation function and largest Lyapunov exponent obey power laws. The critical line and a narrow criticality region close to it move simultaneously to zero confinement strength for infinitely many particles. At the end of the first chaotic window of confinement, there is another phase transition to infinitely dense clusters of finite size that may be termed flocking black holes.Comment: 24 pages, 26 figures, revte

Hybrid layers of etch-and-rinse versus self-etching adhesive systems

Objective: To evaluate the effectiveness in the formation of resin tags, adhesive lateral branches and hybrid layers of five adhesive systems, when bonding to dentine. Material and Methods: Flat dentin surfaces from 25 molars were bonded with several adhesive systems according to the manufacturers? instructions. Composite build-ups were constructed incrementally with Tetric Ceram. The Specimens were sectioned parallel to the long axis. One section was treated with phosphoric acid and sodium hypochlorite in order to reveal the hybrid layer formation. The other section was stored in 30% hydrochloric acid to detect resin tags and adhesive lateral branch formation. Results: The two etch-and-rinse self-priming adhesives exhibited thicker hybrid layers than those found in self-etching adhesive systems. The all-in-one adhesive showed droplet formation between the adhesive and the resin composite. The resin tags formed with the etch-and-rinse adhesives were much longer than those found with the self-etching adhesives. Lateral branch formation was observed in etch-and-rinse adhesives and in one of the self-etch adhesives Clearfil SE Bond (SEB). Conclusion: The formed hybrid layer obtained with the two-step selfetching adhesives and the etch-and-rinse systems were continuous and uniform in thickness. Droplets within the all-in-one adhesive layer may occur as a result of water absorption from dentin through osmosis, and may interfere with proper resin polymerization. Resin tags obtained with SEB and the etch-and-rinse adhesive systems showed lateral branches, which is a sign of proper resin infiltration

Nocardia – Opportunistic chest infection in elderly: A case report

In this rare case a non-immunocompromised patient with old Tuberculosis on low dose of steroids presents with opportunistic infection of a weakly aerobic gram positive acid fast, filamentous bacteria called Nocardia

EPIDEMIOLOGICAL STUDY OF SPANISH RECREATIONAL RUNNERS

The objective of this study was to analyze how different training aspects and biological factors in running affect the probability of suffering an injury and which muscles and joints are more susceptible to develop an injury. A total of 408 subjects, 206 cases and 202 controls, participated in the investigation. The inferior body was more prone to an injury, especially the muscles and tendons associated with the knee and the shank. Several characteristics of the runner and his/her training habits like the sex, age, experience, motivation and mileage have an impact on the injury risk. This information is very useful because biomechanists and coaches can design programs to improve the technique of the runners and reduce the risk of an injury

Strong magnetic response of submicron Silicon particles in the infrared

High-permittivity dielectric particles with resonant magnetic properties are being explored as constitutive elements of new metamaterials and devices in the microwave regime. Magnetic properties of low-loss dielectric nanoparticles in the visible or infrared are not expected due to intrinsic low refractive index of optical materials in these regimes. Here we analyze the dipolar electric and magnetic response of loss-less dielectric spheres made of moderate permittivity materials. For low material refractive index there are no sharp resonances due to strong overlapping between different multipole contributions. However, we find that Silicon particles with refractive index 3.5 and radius approx. 200nm present a dipolar and strong magnetic resonant response in telecom and near-infrared frequencies, (i.e. at wavelengths approx. 1.2-2 micrometer). Moreover, the light scattered by these Si particles can be perfectly described by dipolar electric and magnetic fields, quadrupolar and higher order contributions being negligible.Comment: 10 pages, 5 figure

Medicaments: quin, quan, com...Projecte d’Aprenentatge i Servei per a secundària. Guia didàctica

Il·lustracions originals de Roser Bosch Mestres.La unitat didàctica que hem realitzat té com objectiu principal dissenyar un projecte d’Aprenentatge i Servei (APS) centrat en el bon ús dels medicaments. El projecte es caracteritza per ser una proposta educativa adreçada a joves d’ESO o de 1r curs de Batxillerat que combina activitats d’aprenentatge amb activitats de servei a la comunitat. Pensem que és un enfocament metodològic que ajuda a desenvolupar i a assolir determinades competències bàsiques, a la vegada que motiva l’alumnat, ja que es presenta un ensenyament contextualitzat i significatiu per a la comunitat. Els projectes d’APS responen a una necessitat concreta i rellevant de l’entorn social i, sempre que es pugui, ha d’implicar un acord de col·laboració entre diferents agents o institucions socials que possibilitin aquesta reciprocitat de beneficis d’aprenentatge i de servei. En aquest cas hem treballat com “partners” amb el Col·legi de farmacèutics, amb les farmàcies del barri i amb el SIGRE (responsable del reciclatge dels medicaments)