arXiv subjects

Jozef Černák

Publications and source records attributed to Jozef Černák.

8 recordsLinked to original sources

arXiv2026

Slovakia's Mass Testing: A Critical Look at the Negative Effects

This e-letter re-evaluates the epidemiological impact of nationwide mass antigen testing in Slovakia. While initial reports \cite{Pavelka} proposed a causal link between these campaigns and declining viral prevalence, granular re-analysis reveals a significant temporal mismatch. We argue that the proclaimed success represents a conceptual nexus lacking empirical support; shifts in the effective reproduction number ($R_t$), case trajectories, and mortality rates do not align with the testing rounds. Crucially, the mortality-to-hospital admission ratio exhibits a distinct inverse relationship with the interventions. Rather than providing a clinical benefit, the testing campaigns were followed by increased mortality and a strained healthcare system. We contend that these adverse outcomes were a direct consequence of the testing policy, which sustained higher overall mobility levels compared to the United Kingdom. By overattributing causality to mass testing, a spurious nexus was constructed, obscuring the true drivers of the pandemic and its socio-economic consequences.

physics.bio-ph↗

arXiv2021

Spatio-temporal dynamics of outbreak on a lattice with quenched mobility patterns

We have designed a computational model of a virus spread near the outbreak threshold. Using computer simulation we studied the Susceptible - Infected - Recovered (SIR) process where in consequence of a force of habit that is manifested by the population mobility patterns, the recovered persons create the spatio-temporal patterns as the barriers to a virus transmission. The results show a spontaneous stopping of the virus spread without a need to infect the whole population, a non-trivial random noise of daily count of infected cases, and power laws of a cumulative count of infected cases. Outbreak evolution strongly depends on the initial conditions thus we concluded that the model has the features of chaotic systems that makes it difficult to predict its behaviors.

q-bio.PE↗

arXiv2021

The questionable impact of population-wide public testing in reducing SARS-CoV-2 infection prevalence in the Slovak Republic

Mina and Andersen, authors of the Perspectives in Science: COVID-19 Testing: One Size Does Not Fit All have referred to results and adopted conclusions from recently published governmental report Pavelka et al. "The effectiveness of population wide, rapid antigen test based screening in reducing SARS-CoV-2 infection prevalence in Slovakia" without critical consideration, and rigorous verification. We demonstrate that the authors refer to conclusions that are not supported by experimental data. Further, there is a lack of objective, independent information and studies regarding the widespread, public testing program currently in force in the Slovak Republic. We offer an alternative explanation of observed data as they have been provided by the Slovak Republic government to fill this information gap. We also provide explanations and conclusions that more accurately describe viral spread dynamics. Drawing from available public data and our simple but rigorous analysis, we show that it is not possible to make clear conclusions about any positive impact of the public testing program in the Slovak Republic. In particular, it is not possible to conclude that this testing program forces the curve down for the SARS-CoV-2 virus outbreak. We think that Pavelka et al. did not consider many fundamental phenomena in their proposed computer simulations and data analysis - in particular: the complexity of SARS-CoV-2 virus spread. In complex spatio-temporal dynamical systems, small spatio-temporal fluctuations can dramatically change the dynamics of virus spreading on large scales.

q-bio.PE↗

arXiv2017

Low fertility rate reversal: a feature of interactions between Biological and Economic systems

An empirical relation indicates that an increase of living standard decreases the Total Fertility Rate (TFR), but this trend was broken in highly developed countries in 2005. The reversal of the TFR was associated with the continuous economic and social development expressed by the Human Development Index (HDI). We have investigated how universal and persistent the TFR reversal is. The results show that in highly developed countries, $ \mathrm{HDI}>0.85 $, the TFR and the HDI are not correlated in 2010-2014. Detailed analyses of correlations and differences of the TFR and the HDI indicate a decrease of the TFR if the HDI increases in this period. However, we found that a reversal of the TFR as a consequence of economic development started at medium levels of the HDI, i.e. $ 0.575<\mathrm{HDI}<0.85 $, in many countries. Our results show a transient nature of the TFR reversal in highly developed countries in 2010-2014 and a relative stable trend of the TFR increase in medium developed countries in longer time periods. We believe that knowledge of the fundamental nature of the TFR is very important for the survival of medium and highly developed societies.

physics.soc-ph↗

arXiv2017

The evolutionary approach to understand human low fertility phenomenon

Is it possible to reverse the low total fertility rate (TFR) in the developed world? Using a hypothetical model of population we have analysed the decline of the TFR which have took place in the background of ongoing global economic changes, and a liberalization process after the end of the Cold War. These phenomena have affected more than 110 millions of inhabitants of Central Europe and the Baltics and approximately 80 millions of inhabitants in Germany. The model has features of complex and evolving system of interacting individuals, and it enables to investigate a broad spectrum of input factors on individual decisions to limit the offspring. In the case of the TFR <1.5, our initial analysis show a need of radical changes of the global economy that will stimulate series of self-regulations of demographic processes and evolution toward the safe TFR>2.1. The changes should stimulate more uniform spatial distribution of wealth, capital and usage. They will increase a number of self-sufficient and cooperative territories, to decrease the income inequality, to decrease labour and social mobilities. Societies should investigate the impacts of economic regulations and actions on the TFR trends in advance and take into account a biological nature of women more responsible.

physics.soc-ph↗

arXiv2014

Magnetoresistance of composites based on graphitic disks and cones

We have studied the magnetotransport of conical and disk-shaped nanocarbon particles in magnetic fields $\left|B\right|\leq9\:\mathrm{T}$ at temperatures $2\leq T\leq300\:\mathrm{K}$ to characterize electron scattering in a three dimensional disordered material of multilayered quasi 2D and 3D carbon nanoparticles. The microstructure of the particles was modified by graphitization at temperatures $1600^{\circ}\mathrm{C}$ and $2700^{\circ}\mathrm{C}$. We find clear correlations between the microstructure as seen in transmission electron microscopy and the magnetotransport properties of the particles. The magnetoresistance measurements showed a metallic nature of samples and positive magnetoconductance which is a signature of weak localization in disordered systems. We find that the magnetoconductance at low temperatures resembles quantum transport in single-layer graphene despite the fact that the samples are macroscopic and three dimensional, consisting of stacked and layered particles, which are randomly oriented in the bulk sample. This graphene-like behaviour is attributed to the very weak interlayer coupling between the graphene layers.

cond-mat.mes-hall↗

arXiv2010

Non-Abelian self-organized criticality model with one stochastic site in any avalanche shows multifractal scaling

I have proposed a\textit{non-Abelian}and stochastic self-organized criticality model in which each avalanche contains one stochastic site and all remaining sites in the avalanche are deterministic with a constant threshold $E_{c}^{I}$. Studies of avalanche structures, waves and autocorrelations, size moments and probability distribution functions of avalanche size, for the thresholds $4\leq E_{c}^{I}\leq256$, were performed. The shell-like avalanche structures, correlated waves within avalanches, complex size moments and probability distribution functions show multifractal scaling like the \textit{Abelian} and deterministic BTW model despite the fact that the model is \textit{non-Abelian}and stochastic with unbalanced relaxation rules at each stochastic site.

cond-mat.stat-mech↗

arXiv2008

Aggregation of magnetic holes in a rotating magnetic field

We have experimentally investigated field induced aggregation of nonmagnetic particles confined in a magnetic fluid layer when rotating magnetic fields were applied. After application of a magnetic field rotating in the plane of the fluid layer, the single particles start to form two-dimensional (2D) clusters, like doublets, triangels, and more complex structures. These clusters aggregated again and again to form bigger clusters. During this nonequilibrium process, a broad range of cluster sizes was formed, and the scaling exponents, $z$ and $z'$, of the number of clusters $N(t)\sim t^{z'}$and average cluster size $S(t)\sim t^{z}$ were calculated. The process could be characterized as diffusion limited cluster-cluster aggregation. We have found that all sizes of clusters that occured during an experiment, fall on a single curve as the dynamic scaling theory predicts. Hovewer, the characteristic scaling exponents $z',\: z$ and crossover exponents $Δ$ were not universal. A particle tracking method was used to find the dependence of the diffusion coefficients $D_{s}$ on cluster size $s$. The cluster motions show features of \textit{\emph{Brownian}} motion. The average diffusion coefficients $ $ depend on the cluster sizes $s$ as a power law $ \propto s^γ$ where values of $γ$ as different as $γ=-0.62\pm0.19$ and $γ=-2.08\pm0. were found in two of the experiments.

cond-mat.soft↗