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Qualitative features of a NPZ-Model. NPZ模型的定性特征。
Q2 Agricultural and Biological Sciences Pub Date : 2021-03-14 DOI: 10.11145/J.BIOMATH.2020.01.067
Yaya Youssouf Yaya, D. Ngom, Mamadou Sy
Qualitative study of higher order non linear dynamical systems? is a rewarding experience and a great challenge. This reflective paper is an attempt to deeply analyze interaction features between nutrients, phytoplanktons and zooplanktons by building a so-called NPZ-Model. We used classical methods (of Lyapunov, Hopf, etc.) to examine existence, positivity, boundedness and stability of solutions. Our main contribution is the implementation of a meaningful space parameter that simultaneously guarantees instability of equilibria at the border and? stability of the internal equilibrium. In the case of internal equilibrium instability, we observed the emergence of limit cycle which means the existence of periodical solutions.
高阶非线性动力系统的定性研究?这是一次有益的经历,也是一次巨大的挑战。这篇反思性的论文试图通过建立一个所谓的NPZ模型来深入分析营养物质、浮游植物和浮游动物之间的相互作用特征。我们使用经典的方法(李雅普诺夫、霍普夫等)来检验解的存在性、正性、有界性和稳定性。我们的主要贡献是实现了一个有意义的空间参数,该参数同时保证了边界平衡的不稳定性?内部平衡的稳定性。在内部平衡不稳定的情况下,我们观察到极限环的出现,这意味着周期解的存在。
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引用次数: 0
Accounting for multi-delay effects in an HIV-1 infection model with saturated infection rate, recovery and proliferation of host cells 考虑HIV-1感染模型的多重延迟效应与饱和感染率,宿主细胞的恢复和增殖
Q2 Agricultural and Biological Sciences Pub Date : 2020-12-31 DOI: 10.11145/j.biomath.2020.12.297
D. Adak, N. Bairagi, R. Hakl
Biological models inherently contain delay. Mathematical analysis of a delay-induced model is, however, more difficult compare to its non-delayed counterpart. Difficulties multiply if the model contains multiple delays. In this paper, we analyze a realistic HIV-1 infection model in the presence and absence of multiple delays. We consider self-proliferation of CD4+T cells, nonlinear saturated infection rate and recovery of infected cells due to incomplete reverse transcription in a basic HIV-1 in-host model and incorporate multiple delays to account for successful viral entry and subsequent virus reproduction from the infected cell. Both of delayed and non-delayed system becomes disease-free if the basic reproduction number is less than unity. In the absence of delays, the infected equilibrium is shown to be locally asymptotically stable under some parametric space and unstable otherwise. The system may show unstable oscillatory behaviour in the presence of either delay even when the non-delayed system is stable. The second delay further enhances the instability of the endemic equilibrium which is otherwise stable in the presence of a single delay. Numerical results are shown to be in agreement with the analytical results and reflect quite realistic dynamics observed in HIV-1 infected individuals.
生物模型固有地包含延迟。然而,与非延迟模型相比,延迟诱导模型的数学分析更为困难。如果模型包含多个延迟,困难会成倍增加。在本文中,我们分析了存在和不存在多重延迟的现实HIV-1感染模型。在一个基本的HIV-1宿主模型中,我们考虑了CD4+T细胞的自我增殖、非线性饱和感染率以及由于不完全逆转录而导致的感染细胞的恢复,并纳入了多个延迟来解释病毒成功进入和随后病毒从感染细胞繁殖的原因。当基本繁殖数小于1时,延迟系统和非延迟系统都成为无病系统。在不存在时滞的情况下,被感染的平衡点在某些参数空间下是局部渐近稳定的,在其他参数空间下是不稳定的。当非延迟系统是稳定的时,系统在任何一种延迟的存在下都可能表现出不稳定的振荡行为。第二次延迟进一步增强了地方性平衡的不稳定性,而地方性平衡在存在单一延迟时是稳定的。数值结果与分析结果一致,反映了在HIV-1感染个体中观察到的相当真实的动态。
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引用次数: 1
Modelling the impacts of lockdown and isolation on the eradication of COVID-19 模拟封锁和隔离对根除新冠肺炎的影响
Q2 Agricultural and Biological Sciences Pub Date : 2020-10-26 DOI: 10.11145/j.biomath.2020.09.107
J. Ndam
A model describing the dynamics of COVID-19 is formulated and examined. The model is meant to address the impacts of lockdown and social isolation as strategies for the eradication of the pandemic. Local stability analysis indicate that the equilibria are locally-asymptotically stable for R0<1 and R_0>1 for the disease-free equilibrium and the endemic equilibrium respectively. Numerical simulations of the model equations show that lockdown is a more effective strategy in the eradication of the disease than social isolation. However, strict enforcement of both strategies is the most effective means that could end the disease within a shorter period of time.
建立并检验了一个描述COVID-19动态的模型。该模型旨在解决作为根除大流行战略的封锁和社会隔离的影响。局部稳定性分析表明,无病平衡和地方病平衡对R01分别是局部渐近稳定的。模型方程的数值模拟表明,在消除疾病方面,封锁是比社会隔离更有效的策略。然而,严格执行这两项战略是可以在较短时间内结束这一疾病的最有效手段。
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引用次数: 5
The impact of infected T lymphocyte burst rate and viral shedding rate on optimal treatment scheduling in a human immunodeficiency virus infection 感染T淋巴细胞破裂率和病毒脱落率对人类免疫缺陷病毒感染最佳治疗计划的影响
Q2 Agricultural and Biological Sciences Pub Date : 2020-09-12 DOI: 10.11145/J.BIOMATH.2020.08.173
Anuraag Bukkuri
We consider a mathematical model of human immunodeficiency virus (HIV) infection dynamics of T lymphocyte (T cell), infected T cell, and viral populations under reverse transcriptase inhibitor (RTI) andprotease inhibitor (PI) treatment. Existence, uniqueness, and characterization of optimal treatment profiles which minimize total amount of drug used, viral, and infected T cell populations, while maximizing levels of T cells are determined analytically. Numerical optimal control experiments are also performed to illustrate how burst rate of infected T cells and shedding rate of virions impact optimal treatment profiles. Finally, a sensitivity analysis is performed to detect how model input parameters contribute to output variance.
我们考虑了逆转录酶抑制剂(RTI)和蛋白酶抑制剂(PI)治疗下T淋巴细胞(T细胞)、感染的T细胞和病毒群的人类免疫缺陷病毒(HIV)感染动力学的数学模型。通过分析确定最佳治疗方案的存在性、唯一性和特征,该方案最大限度地减少所用药物、病毒和感染的T细胞群的总量,同时最大限度地提高T细胞水平。还进行了数值优化控制实验,以说明受感染的T细胞的爆发率和病毒粒子的脱落率如何影响最佳治疗方案。最后,进行灵敏度分析,以检测模型输入参数对输出方差的贡献。
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引用次数: 0
Robust numerical method for a singularly perturbed problem arising in the modelling of enzyme kinetics 酶动力学模型中奇异摄动问题的鲁棒数值方法
Q2 Agricultural and Biological Sciences Pub Date : 2020-09-12 DOI: 10.11145/J.BIOMATH.2020.08.227
John J. H. Miller, E. O'Riordan
A system of two coupled nonlinear initial value equations, arising in the mathematical modelling of enzyme kinetics, is examined. The system is singularly perturbed and one of the components will contain steep gradients. A priori parameter explicit bounds on the two components are established. A numerical method incorporating a specially constructed piecewise-uniform mesh is used to generate numerical approximations, which are shown to converge pointwise to the continuous solution irrespective of the size of the singular perturbation parameter. Numerical results are presented to illustrate the computational performance of the numerical method. The numerical method is also remarkably simple to implement. 
研究了酶动力学数学模型中出现的两个耦合非线性初值方程组。系统是奇异摄动的,其中一个组件将包含陡峭的梯度。建立了两个分量的先验参数显式边界。采用一种结合特殊构造的分段均匀网格的数值方法来生成数值逼近,结果表明,与奇异扰动参数的大小无关,该数值逼近点向连续解收敛。数值结果说明了数值方法的计算性能。数值方法的实现也非常简单。
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引用次数: 2
Analysis of a virus-resistant HIV-1 model with behavior change in non-progressors 具有非进展者行为改变的病毒抗性HIV-1模型分析
Q2 Agricultural and Biological Sciences Pub Date : 2020-08-08 DOI: 10.11145/j.biomath.2020.06.143
Musa Rabiu, R. Willie, N. Parumasur
We develop a virus-resistant HIV-1 mathematical model with behavioural change in HIV-1 resistant non-progressors. The model has both disease-free and endemic equilibrium points that are proved to be locally asymptotically stable depending on the value of the associated reproduction numbers. In both models, a non-linear Goh{Volterra Lyapunov function was used to prove that the endemic equilibrium point is globally asymptotically stable for special case while the method of Castillo-Chavez was used to prove the global asymptotic stability of the disease-free equilibrium point. In both the analytic and numerical results, this study shows that in the context of resistance to HIV/AIDS, total abstinence can also play an important role in protection against this notorious infectious disease.
我们开发了一个具有病毒抗性的HIV-1数学模型,其中包含HIV-1抗性非进展者的行为变化。该模型同时具有无病平衡点和地方性平衡点,并根据相关繁殖数的值证明它们是局部渐近稳定的。在这两个模型中,采用非线性Goh{Volterra Lyapunov函数证明了特殊情况下的地方病平衡点是全局渐近稳定的,采用Castillo-Chavez方法证明了无病平衡点的全局渐近稳定。在分析和数值结果中,本研究表明,在抵抗艾滋病毒/艾滋病的背景下,完全禁欲也可以在预防这种臭名昭着的传染病方面发挥重要作用。
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引用次数: 6
COVID-19 propagation mathematical modeling: the case of Senegal COVID-19传播数学建模:以塞内加尔为例
Q2 Agricultural and Biological Sciences Pub Date : 2020-06-18 DOI: 10.20944/preprints202006.0224.v1
Mouhamadou Diaby, Oumar Diop, A. Konté, A. Sène
The outburst of the COVID-19 pandemic has raised several questions leading to a complex system in terms of modeling. Indeed, the modeling of the epidemic, at the level of a country, needs considering each of the different sources of contamination as well as the public health authorities strategy, in a specific way. With this in mind, in the present paper, we develop a mathematical model of the COVID-19 epidemic in Senegal. In the model, the population is subdivided into five compartments: susceptible, infected but asymptomatic, symptomatic, quarantined, and recovered immune people. In addition, due to its important impact on the propagation of the disease, we add one more variable: the number of infected objects. Therefore, the model corresponds to a system of six non-linear ordinary differential equations we submit to an analytical study to prove the relevancy of the model,  simulate the evolution of the epidemic, and retrieve epidemiological parameters, namely the infection rate and the basic reproduction number. Based on the senegalese territory COVID-19 data, we simulate various scenarios as for the evolution of the epidemic in the country, in order to predict the peak and its magnitude with regard to the application of barrier measures. We also explore the option of collective immunity with special protection for vulnerable people. In doing so, non-available parameters are identified using some mathematical identification technics.
新冠肺炎疫情的爆发引发了几个问题,导致了一个复杂的建模系统。事实上,在一个国家层面上,流行病的建模需要以特定的方式考虑每种不同的污染源以及公共卫生当局的战略。考虑到这一点,在本文中,我们开发了塞内加尔新冠肺炎疫情的数学模型。在该模型中,人群被细分为五个部分:易感人群、感染但无症状人群、有症状人群、隔离人群和免疫康复人群。此外,由于其对疾病传播的重要影响,我们增加了一个变量:感染对象的数量。因此,该模型对应于我们提交给分析研究的六个非线性常微分方程组,以证明该模型的相关性,模拟疫情的演变,并检索流行病学参数,即感染率和基本繁殖数。根据塞内加尔领土新冠肺炎数据,我们模拟了该国疫情演变的各种情景,以预测屏障措施应用方面的峰值及其规模。我们还探讨了为弱势群体提供特殊保护的集体豁免方案。在这样做的过程中,使用一些数学识别技术来识别不可用的参数。
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引用次数: 2
A new class of activation functions. Some related problems and applications 一类新的激活函数。相关问题及应用
Q2 Agricultural and Biological Sciences Pub Date : 2020-05-17 DOI: 10.11145/j.biomath.2020.05.033
N. Kyurkchiev
The cumulative distribution function (cdf) of the discrete two--parameter bathtub hazard distribution has important role in the fields of population dynamics, reliability analysis and life testing experiments. Also of interest to the specialists is the task of approximating the Heaviside function by new (cdf) in Hausdorff sense. We define new activation function and family of new recurrence generated functions and study the ''saturation'' by these families. In this paper we analyze some intrinsic properties of the new Topp-Leone-G-Family with baseline ''deterministic-type'' (cdf) - (NTLG-DT). Some numerical examples with real data from Biostatistics, Population dynamics and Signal theory, illustrating our results are given. It is shown that the study of the two characteristics - "confidential curves" and ''super saturation'' is a must when choosing the right model. Some related problems are discussed, as an example to the Approximation Theory.
离散双参数浴缸危险性分布的累积分布函数在群体动力学、可靠性分析和寿命试验等领域具有重要作用。专家们还感兴趣的是用Hausdorff意义上的new(cdf)逼近Heaviside函数的任务。我们定义了新的激活函数和新的递推生成函数家族,并研究了这些家族的“饱和度”。在本文中,我们分析了新的Topp-Leone-G家族的一些内在性质,其基线为“确定型”(cdf)-(NTLG-DT)。用生物统计学、种群动力学和信号理论的实际数据给出了一些数值例子,说明了我们的结果。结果表明,在选择合适的模型时,必须研究“机密曲线”和“超饱和”这两个特性。以近似理论为例,讨论了一些相关问题。
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引用次数: 5
The big unknown: The asymptomatic spread of COVID-19 最大的未知:COVID-19的无症状传播
Q2 Agricultural and Biological Sciences Pub Date : 2020-05-11 DOI: 10.11145/j.biomath.2020.05.103
R. Anguelov, J. Banasiak, C. Bright, J. Lubuma, R. Ouifki
The paper draws attention to the asymptomatic and mildly symptomatic cases of COVID-19, which, according to some reports, may constitute a large fraction of the infected individuals. These cases are often unreported and are not captured in the total number of confirmed cases communicated daily. On the one hand, this group may play a significant role in the spread of the infection, as asymptomatic cases are seldom detected  and quarantined. On the other hand, it may play a significant role in disease extinction by contributing to the development of sufficient herd immunity.
文章提请注意无症状和轻度症状的新冠肺炎病例,根据一些报道,这可能占感染者的很大一部分。这些病例往往没有得到报告,也没有包括在每天通报的确诊病例总数中。一方面,这一群体可能在感染的传播中发挥重要作用,因为很少发现和隔离无症状病例。另一方面,它可能通过促进群体免疫力的发展而在疾病灭绝中发挥重要作用。
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引用次数: 22
COVID-19 Research Communications (Editorial) COVID-19研究通讯(社论)
Q2 Agricultural and Biological Sciences Pub Date : 2020-05-04 DOI: 10.11145/j.biomath.2020.05.047
H. Kojouharov
The goal of the series is to provide a platform for rapid communication and exchange of ideas concerning the COVID-19 epidemic. It is new and unlike the known virus-induced diseases. There is a significant research effort, including mathematical modelling, to understand the characteristics of the virus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) and the epidemiological dynamics of COVID-19, the disease caused by it. Due to their novelty, the research is often likely to produce results only on specific aspects of the disease, provide just partial answers to research questions, or collect evidence for formulating hypothesis yet to be tested. We believe, however, that the significance of the pandemic for the human population makes it essential to share even such partial results as soon as they are available to facilitate the advancement of the research on this disease. While eventually, a more comprehensive picture of both the virus and the disease will emerge, even incomplete but timely and scientifically-based information will help the authorities to make sound decisions on the course of action during the epidemic. For the series, we invite publications on any aspect of the COVID-19 epidemic. Specifically, the series aims to cover • the biological research, providing an understanding of the relevant structures and causal relationships in the epidemiological environment, which can facilitate mathematical or statistical modelling, • mathematical models of the structures, causal interactions and epidemiological data, and their analysis, • mathematical models and analysis of the socio-economic aspects of the pandemic, • any new mathematical methods, applicable to the study of any of the mentioned topics. All submissions to the series will be prioritised for a fast peer-review.
该系列的目标是为有关新冠肺炎疫情的快速沟通和思想交流提供一个平台。它是新的,与已知的病毒引起的疾病不同。有大量的研究工作,包括数学模型,以了解严重急性呼吸综合征冠状病毒2型病毒的特征及其引起的疾病新冠肺炎的流行病学动态,只提供研究问题的部分答案,或者收集证据来提出有待检验的假设。然而,我们认为,由于这场大流行病对人类的重要性,即使是这样的部分结果,也必须在获得后尽快分享,以促进对这种疾病的研究进展。虽然最终会对病毒和疾病产生更全面的了解,但即使是不完整但及时且基于科学的信息,也将有助于当局在疫情期间就行动方案做出正确的决定。对于该系列,我们邀请有关新冠肺炎疫情任何方面的出版物。具体而言,该系列旨在涵盖•生物学研究,提供对流行病学环境中相关结构和因果关系的理解,这有助于数学或统计建模,•结构、因果相互作用和流行病学数据的数学模型及其分析,•疫情社会经济方面的数学模型和分析,•适用于上述任何主题研究的任何新数学方法。所有提交给该系列的作品都将优先进行快速同行评审。
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引用次数: 0
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