Universality in spectral condensation

Self-organization is the spontaneous formation of spatial, temporal, or spatiotemporal patterns in complex systems far from equilibrium. During such self-organization, energy distributed in a broadband of frequencies gets condensed into a dominant mode, analogous to a condensation phenomena. We call this phenomenon spectral condensation and study its occurrence in fluid mechanical, optical and electronic systems. We define a set of spectral measures to quantify this condensation spanning several dynamical systems. Further, we uncover an inverse power law behaviour of spectral measures with the power corresponding to the dominant peak in the power spectrum in all the aforementioned systems.Comment: 5 pages, 3 figure

Universality in spectral condensation

Self-organization is the spontaneous formation of spatial, temporal, or spatiotemporal patterns in complex systems far from equilibrium. During such self-organization, energy distributed in a broadband of frequencies gets condensed into a dominant mode, analogous to a condensation phenomenon. We call this phenomenon spectral condensation and study its occurrence in fluid mechanical, optical and electronic systems. We define a set of spectral measures to quantify this condensation spanning several dynamical systems. Further, we uncover an inverse power law behaviour of spectral measures with the power corresponding to the dominant peak in the power spectrum in all the aforementioned systems

Neurological manifestations of COVID-19 in adults and children

Different neurological manifestations of coronavirus disease 2019 (COVID-19) in adults and children and their impact have not been well characterized. We aimed to determine the prevalence of neurological manifestations and in-hospital complications among hospitalized COVID-19 patients and ascertain differences between adults and children. We conducted a prospective multicentre observational study using the International Severe Acute Respiratory and emerging Infection Consortium (ISARIC) cohort across 1507 sites worldwide from 30 January 2020 to 25 May 2021. Analyses of neurological manifestations and neurological complications considered unadjusted prevalence estimates for predefined patient subgroups, and adjusted estimates as a function of patient age and time of hospitalization using generalized linear models. Overall, 161 239 patients (158 267 adults; 2972 children) hospitalized with COVID-19 and assessed for neurological manifestations and complications were included. In adults and children, the most frequent neurological manifestations at admission were fatigue (adults: 37.4%; children: 20.4%), altered consciousness (20.9%; 6.8%), myalgia (16.9%; 7.6%), dysgeusia (7.4%; 1.9%), anosmia (6.0%; 2.2%) and seizure (1.1%; 5.2%). In adults, the most frequent in-hospital neurological complications were stroke (1.5%), seizure (1%) and CNS infection (0.2%). Each occurred more frequently in intensive care unit (ICU) than in non-ICU patients. In children, seizure was the only neurological complication to occur more frequently in ICU versus non-ICU (7.1% versus 2.3%, P < 0.001). Stroke prevalence increased with increasing age, while CNS infection and seizure steadily decreased with age. There was a dramatic decrease in stroke over time during the pandemic. Hypertension, chronic neurological disease and the use of extracorporeal membrane oxygenation were associated with increased risk of stroke. Altered consciousness was associated with CNS infection, seizure and stroke. All in-hospital neurological complications were associated with increased odds of death. The likelihood of death rose with increasing age, especially after 25 years of age. In conclusion, adults and children have different neurological manifestations and in-hospital complications associated with COVID-19. Stroke risk increased with increasing age, while CNS infection and seizure risk decreased with age

Performance Evaluation of Field Exposed Painted Constructional Steels

The major protective coatings applied to structural steelwork are paints, metal coatings and combinations of both. The choice is partly governed by the actual enviro-nmental conditions and partly by economic considerations. Organic coatings used on steel provide an effective barrier protection by isolating steel from the attacking species. The barrier properties of the coating are impro-ved by increased thickness, by the presence of pigments and fillers that increase the diffusion path for water and oxygen, and by the ability to resist degradation. Degradation allows access of reactants to the coating / substrate interface without the necessity for diffusion through the coating and it is an electrochemical process which follows the same principles as corrosion of uncoated steel. As coatings age in a corrosive environment, the interconnecting network of pores within the coating event-ually become saturated with water, salts, etc., exposing the metal substrate to a corrosive environment. An impor-tant property of a coating is its resistance to water penetration and there is a direct correlation between resistances and the ability of the coating to protect the underlying steel from corrosion. A generic three coat paint system was taken from a leading paint company for carrying out exposure tests

Strange nonchaotic attractor in memristor-based van der Pol oscillator

We report the occurrence of a strange nonchaotic attractor in a quasi-periodically driven memristor based van der Pol oscillator. The strange nonchaotic attractors (SNAs) appear in the system with suitable choices of parameters. While varying the amplitude of one of the external forces, we observe that the system torus gets fractalized and the SNAs are emerging. We use both the qualitative and quantitative characterization methods, such as Lyapunov exponent, the variance of finite-time Lyapunov exponent, Poincaré maps, singular continuous spectrum, and phase sensitivity exponent to confirm the SNAs in the system

Strange nonchaos in self-excited singing flames

We report the first experimental evidence of a strange nonchaotic attractor (SNA) in the natural dynamics of a self-excited laboratory-scale system. In the previous experimental studies, the birth of a SNA was observed in quasiperiodically forced systems; however, such evidence of a SNA in an autonomous laboratory system is yet to be reported. We discover the presence of a SNA between the attractors of quasiperiodicity and chaos through a fractalization route in a laboratory thermoacoustic system. The observed dynamical transitions from order to chaos via a SNA is confirmed through various nonlinear characterization methods prescribed for the detection of a SNA

Dragon-king extreme events as precursors for catastrophic transition

Unexpected catastrophic transitions are often observed in complex systems. However, the prediction of such transitions is difficult in practice. Here, we find a special kind of extreme events with a dragon-king probability distribution that occur just prior to a catastrophic transition and, hence, can serve as its precursor. To illustrate the application of dragon kings as a precursor, we consider a practical experimental thermo-fluid system and a theoretical model of coupled logistic maps with quasi-periodic forcing, both systems displaying a catastrophic transition