A wastewater-based harmless delay differential equation model to understand the emergence of SARS-CoV-2 variants

We consider the dynamics of a virus spreading through a population that produces a mutant strain with the ability to infect individuals that were infected with the established strain. Temporary cross-immunity is included using a time delay, but is found to be a harmless delay. We provide some sufficient conditions that guarantee local and global asymptotic stability of the disease-free equilibrium and the two boundary equilibria when the two strains outcompete one another. It is shown that, due to the immune evasion of the emerging strain, the reproduction number of the emerging strain must be significantly lower than that of the established strain for the local stability of the established-strain-only boundary equilibrium. To analyze the unique coexistence equilibrium, we apply a quasi-steady-state argument to reduce the full model to a two-dimensional one that exhibits a global asymptotically stable established-strain-only equilibrium or global asymptotically stable coexistence equilibrium. Our results indicate that the basic reproduction numbers of both strains govern the overall dynamics, but in nontrivial ways due to the inclusion of cross-immunity. The model is applied to study the emergence of the SARS-CoV-2 Delta variant in the presence of the Alpha variant using wastewater surveillance data from the Deer Island Treatment Plant in Massachusetts, USA

Mathematics of a single-locus model for assessing the impacts of pyrethroid resistance and temperature on population abundance of malaria mosquitoes

Please read abstract in the article.http://www.keaipublishing.com/en/journals/infectious-disease-modelling/Mathematics and Applied Mathematic

Dynamics of COVID-19 pandemic in India and Pakistan : a metapopulation modelling approach

India has been the latest global epicenter for COVID-19, a novel coronavirus disease that emerged in China in late 2019.We present a base mathematical model for the transmission dynamics of COVID-19 in India and its neighbor, Pakistan. The base model was rigorously analyzed and parameterized using cumulative COVID-19 mortality data from each of the two countries. The model was used to assess the population-level impact of the control and mitigation strategies implemented in the two countries (notably non-pharmaceutical interventions). Numerical simulations of the basic model indicate that, based on the current baseline levels of the control and mitigation strategies implemented, the pandemic trajectory in India is on a downward trend. This downward trend will be reversed, and India will be recording mild outbreaks, if the control and mitigation strategies are relaxed from their current levels. By early September 2021, our simulations suggest that India could record up to 460,000 cumulative deaths under baseline levels of the implemented control strategies, while Pakistan (where the pandemic is comparatively milder) could see over 24,000 cumulative deaths at current mitigation levels. The basic model was extended to assess the impact of back-and-forth mobility between the two countries. Simulations of the resulting metapopulation model show that the burden of the COVID-19 pandemic in Pakistan increases with increasing values of the average time residents of India spend in Pakistan, with daily mortality in Pakistan peaking in mid-August to mid-September of 2021. Under the respective baseline control scenarios, our simulations show that the backand- forth mobility between India and Pakistan could delay the time-to-elimination of the COVID-19 pandemic in India and Pakistan to November 2022 and July 2022, respectively.The Simons Foundation; the National Science Foundation and the Fulbright Scholarship.http://www.keaipublishing.com/idmam2022Mathematics and Applied Mathematic

Pendulum limit, chaos and phase-locking in the dynamics of ac-driven semiconductor superlattices

We describe a limiting case when nonlinear dynamics of an ac-driven semiconductor superlattice in the miniband transport regime is governed by a periodically forced and damped pendulum. We find analytically the conditions for a transition to chaos and consider an influence of temperature on the effect. We also discuss fractional dc voltage states in a superlattice originating from phase-locked states of the pendulum.Comment: 8 pages, no figures. Version2 is strongly revised: new physics, more references. 3 appendixes of this Eprint are absent in the manuscript submitted to journa

Dissipative Chaos in Semiconductor Superlattices

We consider the motion of ballistic electrons in a miniband of a semiconductor superlattice (SSL) under the influence of an external, time-periodic electric field. We use the semi-classical balance-equation approach which incorporates elastic and inelastic scattering (as dissipation) and the self-consistent field generated by the electron motion. The coupling of electrons in the miniband to the self-consistent field produces a cooperative nonlinear oscillatory mode which, when interacting with the oscillatory external field and the intrinsic Bloch-type oscillatory mode, can lead to complicated dynamics, including dissipative chaos. For a range of values of the dissipation parameters we determine the regions in the amplitude-frequency plane of the external field in which chaos can occur. Our results suggest that for terahertz external fields of the amplitudes achieved by present-day free electron lasers, chaos may be observable in SSLs. We clarify the nature of this novel nonlinear dynamics in the superlattice-external field system by exploring analogies to the Dicke model of an ensemble of two-level atoms coupled with a resonant cavity field and to Josephson junctions.Comment: 33 pages, 8 figure

Semiconductor Superlattices: A model system for nonlinear transport

Electric transport in semiconductor superlattices is dominated by pronounced negative differential conductivity. In this report the standard transport theories for superlattices, i.e. miniband conduction, Wannier-Stark-hopping, and sequential tunneling, are reviewed in detail. Their relation to each other is clarified by a comparison with a quantum transport model based on nonequilibrium Green functions. It is demonstrated how the occurrence of negative differential conductivity causes inhomogeneous electric field distributions, yielding either a characteristic sawtooth shape of the current-voltage characteristic or self-sustained current oscillations. An additional ac-voltage in the THz range is included in the theory as well. The results display absolute negative conductance, photon-assisted tunneling, the possibility of gain, and a negative tunneling capacitance.Comment: 121 pages, figures included, to appear in Physics Reports (2001

Empirical modeling of uranium nitride fuels

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Bibliography: leaves 111-112.Not availabl

The determination of the natural convection heat transfer coefficients for a heated cylinder in air at sub-atmospheric pressures

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Not availabl

The Perception of Musical Tension in Percy Grainger’s Irish Tune from County Derry Among Music Majors and Non-Music Majors

The purpose of this study was to determine whether non-major instrumental student musicians at the university level perceive tension in music differently than student musicians majoring in music. Students (N=40) comprised four groups. Group A and Group B consisted of undergraduate students (N=20) who were non-music majors and members of an auditioned university concert band. Group C and D consisted of undergraduate students (N=20) who were music majors. While listening to the selected composition, students registered their individual perception of tension by means of the Digital Affective Response Technology (DART) software. During playback of the selected stimuli, subjects utilize a Likert scale of discrete data points within DART to quantify perceived affective responsiveness from 1 (lowest level) to 10 (highest level). Individual means were then collected from each group (A, B, C, D) and graphed cross-categorically according to level of performance history (majors/nonmajors who have performed (A & C) and majors/non-majors who have not performed (B & D)). An unpaired t-test of combined Groups A and C (t [20] = -1.073, p = .2975) and an unpaired t-test of combined Groups B and D (t [20] = 1.639, p = .1186) indicated no significant difference of perceived tension between the subjects of these groups