modelling

建模
  • 文章类型: Journal Article
    许多研究已经开发或验证了预测模型,以估计食管癌(EC)患者术后肺炎(POP)的可能性。这些模型的质量及其对临床实践和未来研究的适用性的评估仍然未知。本研究系统地评估了食管癌手术患者发生POP的风险预测模型的偏倚风险和适用性。
    PubMed,Embase,WebofScience,科克伦图书馆,护理和相关健康文献累积指数(CINAHL),中国国家知识基础设施(CNKI),中国科技期刊数据库(VIP),从开始到2024年3月12日检索万方数据库和中国生物医学文献数据库。两名研究者独立筛选文献并提取数据。采用预测模型偏差风险评估工具(PROBAST)检查表评估偏差风险和适用性。
    共14项研究,涉及23个模型。这些研究主要发表在2014年至2023年之间。所有研究的适用性都很好。然而,所有研究都表现出偏见的高风险,主要归因于不适当的数据源,样本量不足,对变量和缺失数据的不合理处理,缺乏模型验证。食管癌手术患者POP发生率为14.60%~39.26%。最常用的预测因素是吸烟,年龄,慢性阻塞性肺疾病(COPD),糖尿病,开胸手术的方法。模型间判别范围为0.627~0.850,灵敏度为60.7%~84.0%,特异性为59.1%至83.9%。
    在所有纳入的研究中,据报道,食管癌手术患者POP风险预测模型具有良好的区分度,表明模型性能稳定。然而,根据PROBAST检查表,所有研究均存在较高的偏倚风险.未来的研究应使用预测模型评估工具来改进研究设计,并开发具有更大样本和多中心外部验证的新模型。
    https://www.crd.约克。AC.英国/普劳里,标识符CRD42024527085。
    UNASSIGNED: Numerous studies have developed or validated prediction models to estimate the likelihood of postoperative pneumonia (POP) in esophageal cancer (EC) patients. The quality of these models and the evaluation of their applicability to clinical practice and future research remains unknown. This study systematically evaluated the risk of bias and applicability of risk prediction models for developing POP in patients undergoing esophageal cancer surgery.
    UNASSIGNED: PubMed, Embase, Web of Science, Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL), China National Knowledge Infrastructure (CNKI), China Science and Technology Journal Database (VIP), WanFang Database and Chinese Biomedical Literature Database were searched from inception to March 12, 2024. Two investigators independently screened the literature and extracted data. The Prediction Model Risk of Bias Assessment Tool (PROBAST) checklist was employed to evaluate both the risk of bias and applicability.
    UNASSIGNED: A total of 14 studies involving 23 models were included. These studies were mainly published between 2014 and 2023. The applicability of all studies was good. However, all studies exhibited a high risk of bias, primarily attributed to inappropriate data sources, insufficient sample size, irrational treatment of variables and missing data, and lack of model validation. The incidence of POP in patients undergoing esophageal cancer surgery ranged from 14.60% to 39.26%. The most frequently used predictors were smoking, age, chronic obstructive pulmonary disease(COPD), diabetes mellitus, and methods of thoracotomy. Inter-model discrimination ranged from 0.627 to 0.850, sensitivity ranged between 60.7% and 84.0%, and specificity ranged from 59.1% to 83.9%.
    UNASSIGNED: In all included studies, good discrimination was reported for risk prediction models for POP in patients undergoing esophageal cancer surgery, indicating stable model performance. However, according to the PROBAST checklist, all studies had a high risk of bias. Future studies should use the predictive model assessment tool to improve study design and develop new models with larger samples and multicenter external validation.
    UNASSIGNED: https://www.crd.york.ac.uk/prospero, identifier CRD42024527085.
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  • 文章类型: Journal Article
    数学建模在理解和管理城市供水系统(UWS)中起着至关重要的作用。机械模型通常作为其设计和操作的基础。尽管被广泛收养,机械模型受到动态过程的复杂性和高计算要求的挑战。数据驱动的模型带来了捕捉系统复杂性并降低计算成本的机会,通过利用传感器技术的最新进展提供的丰富数据。然而,可解释性和数据可用性阻碍了它们的广泛采用。本文主张在UWS上下文中应用数据驱动模型的范式转变。将现有的机械知识集成到数据驱动的建模中提供了一种独特的解决方案,可以降低数据需求并增强模型的可解释性。知识知情方法在模型复杂性与数据集大小之间取得平衡,在UWS中实现更高效和可解释的建模。此外,机械和数据驱动模型的集成提供了UWS动力学的更准确表示,解决挥之不去的不确定性,提高建模能力。本文提出了开发和实现知识信息数据驱动建模的观点和概念框架,强调他们在数字时代改善UWS管理的潜力。
    Mathematical modeling plays a crucial role in understanding and managing urban water systems (UWS), with mechanistic models often serving as the foundation for their design and operations. Despite the wide adoptions, mechanistic models are challenged by the complexity of dynamic processes and high computational demands. Data-driven models bring opportunities to capture system complexities and reduce computational cost, by leveraging the abundant data made available by recent advance in sensor technologies. However, the interpretability and data availability hinder their wider adoption. This paper advocates for a paradigm shift in the application of data-driven models within the context of UWS. Integrating existing mechanistic knowledge into data-driven modeling offers a unique solution that reduces data requirements and enhances model interpretability. The knowledge-informed approach balances model complexity with dataset size, enabling more efficient and interpretable modeling in UWS. Furthermore, the integration of mechanistic and data-driven models offers a more accurate representation of UWS dynamics, addressing lingering uncertainties and advancing modelling capabilities. This paper presents perspectives and conceptual framework on developing and implementing knowledge-informed data-driven modeling, highlighting their potential to improve UWS management in the digital era.
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  • 文章类型: Journal Article
    各国建议对青春期少女常规接种一到两剂人乳头瘤病毒(HPV)疫苗,以消除宫颈癌这一公共卫生问题。由于大多数现有疫苗剂量被现有HPV疫苗接种计划的国家(主要是高收入国家)吸收,有限的供应一直留给新的国家引进,直到2022年;其中许多,低收入和中等收入国家死亡率较高。免疫战略专家咨询小组考虑了几种疫苗接种战略,以允许更多国家在供应有限的情况下引入疫苗接种。
    我们研究了从2020年到2030年向100个引进前国家分配有限疫苗剂量的九种策略的影响。使用两种算法来优化癌症死亡的总数,通过有限的剂量(背包和国家特定死亡率的递减顺序)可以避免全球范围内的癌症死亡总数。并使用了未优化的算法(人类发展指数的降序)。
    定期给14岁的女孩接种一剂或两剂疫苗,并在供应不再受限的情况下转向常规的9岁计划,可以防止大多数宫颈癌死亡,不管分配算法。未优化的分配避免了更少的死亡,因为它首先分配给高收入国家,通常具有较低的子宫颈癌死亡率。
    为了在供应有限的情况下优化通过疫苗接种避免的死亡,重要的是优先考虑高负担国家,并首先为年龄较大的女孩接种疫苗。
    谁,比尔和梅林达·盖茨基金会。
    UNASSIGNED: Countries are recommended to immunise adolescent girls routinely with one or two doses of human papillomavirus (HPV) vaccines to eliminate cervical cancer as a public health problem. With most existing vaccine doses absorbed by countries (mostly high-income) with existing HPV vaccination programmes, limited supply has been left for new country introductions until 2022; many of those, low- and middle-income countries with higher mortality. Several vaccination strategies were considered by the Strategic Advisory Group of Experts on Immunization to allow more countries to introduce vaccination despite constrained supplies.
    UNASSIGNED: We examined the impact of nine strategies for allocating limited vaccine doses to 100 pre-introduction countries from 2020 to 2030. Two algorithms were used to optimise the total number of cancer deaths that can be averted worldwide by a limited number of doses (knapsack and decreasing order of country-specific mortality rates), and an unoptimised algorithm (decreasing order of Human Development Index) were used.
    UNASSIGNED: Routinely vaccinating 14-year-old girls with either one or two doses and switching to a routine 9-year-old programme when supply is no longer constrained could prevent the most cervical cancer deaths, regardless of allocation algorithm. The unoptimised allocation averts fewer deaths because it allocates first to higher-income countries, usually with lower cervical cancer mortality.
    UNASSIGNED: To optimise the deaths averted through vaccination when supply is limited, it is important to prioritise high-burden countries and vaccinating older girls first.
    UNASSIGNED: WHO, Bill & Melinda Gates Foundation.
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  • 文章类型: Journal Article
    金属的表面能各向异性对于稳定性和结构至关重要,然而,它的决定因素和结构-性质关系仍然难以捉摸。在这里,我们确定了预测纯金属和合金表面能各向异性的三个关键因素:表面原子密度,配位数和原子半径。我们发现表面几何行列式的耦合规则,确定面心立方(FCC)的表面能各向异性,六角形紧密堆积(HCP)和体心立方(BCC)金属,基本上由晶体结构而不是化学键控制,合金或电子结构。此外,BCC金属表现出依赖于材料的表面能各向异性,取决于原子半径,不像FCC和HCP金属。可以从紧密结合模型框架中的结合特性来理解潜在的机制。我们的方案不仅提供了表面稳定性的新物理图像,而且还提供了材料设计的有用工具。
    Surface-energy anisotropy of metals is crucial for the stability and structure, however, its determining factors and structure-property relationship are still elusive. Herein, we identify three key factors for predicting surface-energy anisotropy of pure metals and alloys: the surface-atom density, coordination numbers and atomic radius. We find that the coupling rules of surface geometric determinants, which determining surface-energy anisotropy of face-centred-cubic (FCC), hexagonal-close-packed (HCP) and body-centred-cubic (BCC) metals, are essentially controlled by the crystal structures instead of chemical bonds, alloying or electronic structures. Furthermore, BCC metals exhibit material-dependent surface-energy anisotropy depending on the atomic radius, unlike FCC and HCP metals. The underlying mechanism can be understood from the bonding properties in the framework of the tight-binding model. Our scheme provides not only a new physical picture of surface stability but also a useful tool for material design.
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  • 文章类型: Journal Article
    2020年,由于COVID-19遏制政策,人为甲烷(CH4)排放量减少,但是大气中CH4的浓度却大大增加。先前的研究表明,这种异常增加与湿地CH4排放量增加和大气CH4汇减少有关。然而,土壤CH4汇变化的影响仍然未知。为了解决这个问题,我们利用基于过程的模型来量化2019年至2020年间陆地生态系统土壤CH4汇的变化。通过使用各种数据集实现模型,我们一直观察到全球土壤CH4汇的增加,与2019年相比,2020年Tg达到0.35±0.06。这种增加主要归因于北部高纬度地区土壤温度升高。我们的结果强调了在陆地生态系统中考虑CH4汇的重要性,因为忽略该成分可能导致对排放增加和大气CH4吸收容量减少的低估。此外,这些发现强调了陆地生态系统中土壤温暖增加在减缓大气中CH4浓度增长方面的潜在作用。
    In 2020, anthropogenic methane (CH4) emissions decreased due to COVID-19 containment policies, but there was a substantial increase in the concentration of atmospheric CH4. Previous research suggested that this abnormal increase was linked to higher wetland CH4 emissions and a decrease in the atmospheric CH4 sink. However, the impact of changes in the soil CH4 sink remained unknown. To address this, we utilized a process-based model to quantify alterations in the soil CH4 sink of terrestrial ecosystems between 2019 and 2020. By implementing the model with various datasets, we consistently observed an increase in the global soil CH4 sink, reaching up to 0.35 ± 0.06 Tg in 2020 compared to 2019. This increase was primarily attributed to warmer soil temperatures in northern high latitudes. Our results emphasize the importance of considering the CH4 sink in terrestrial ecosystems, as neglecting this component can lead to an underestimation of both emission increases and reductions in atmospheric CH4 sink capacity. Furthermore, these findings highlight the potential role of increased soil warmth in terrestrial ecosystems in slowing the growth of CH4 concentrations in the atmosphere.
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  • 文章类型: Journal Article
    浮动光伏(FPV)是一种新兴的可再生能源技术。虽然近年来受到了广泛的关注,对环境影响的理解是有限的。为了解决这个知识差距,我们在FPV阵列和控制开放水域下测量了六个月的水温和气象参数,并建立了反映水能平衡的数值模型。我们的结果表明,FPV阵列引起水温和小气候的日变化。具体来说,我们发现FPV在白天对宿主水体有降温作用,在夜间有保温作用,减少昼夜变化。低于FPV面板的水温的diel振荡落后于开放水域大约两个小时。FPV面板以下的小气候条件也发生了变化,风速下降70%,白天气温升高(平均+2.01°C),夜间气温降低(平均-1.27°C)。值得注意的是,相对湿度的趋势相反(-3.72%,+14.43%)。相关分析表明,受FPV影响的水温程度与当地气候条件有关。数值模型可以捕获模拟数据与实际数据之间的相关系数为0.80的能量平衡特性。FPV板下方的短波辐射和潜热通量显著降低,FPV板发出的长波辐射成为白天的热源之一。这些因素的综合变化主导了FPV面板下方的水能平衡。实测数据和模拟结果为评价FPV系统对水温的影响奠定了基础,能源预算,和水生环境,这也将提供一个更全面的了解FPV系统。
    Floating photovoltaics (FPV) are an emerging renewable energy technology. Although they have received extensive attention in recent years, understanding of their environmental impacts is limited. To address this knowledge gap, we measured water temperature and meteorological parameters for six months under FPV arrays and in the control open water site and constructed a numerical model reflecting the water energy balance. Our results showed that FPV arrays caused diurnal variation in water temperature and microclimate. Specifically, we found that FPV had a cooling effect on their host waterbody during the daytime and a heat preservation effect at night, reducing diurnal variation. The diel oscillation of water temperature below FPV panels lagged behind that of open waters by approximately two hours. The microclimate conditions below FPV panels also changed, with wind speed decreasing by 70%, air temperature increasing during the daytime (averaging +2.01°C) and decreasing at night (averaging -1.27°C). Notably, the trend in relative humidity was the opposite (-3.72%, +14.43%). Correlation analysis showed that the degree of water temperature affected by FPV was related to local climate conditions. The numerical model could capture the energy balance characteristics with a correlation coefficient of 0.80 between the simulated and actual data. The shortwave radiation and latent heat flux below FPV panels was significantly reduced, and the longwave radiation emitted by FPV panels became one of the heat sources during the daytime. The combined variations of these factors dominated the water energy balance below FPV panels. The measured data and simulation results serve as a foundation for evaluating the impact of FPV systems on water temperature, energy budget, and aquatic environment, which would also provide a more comprehensive understanding of FPV systems.
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  • 文章类型: Journal Article
    农产品的含水率检测是质量控制的关键,处理效率和存储管理。测试谷子水分含量可确保谷子质量稳定,并帮助农民确定最佳收获时间。设计了一种基于STM32和PCAP01电容数字转换器芯片的差分电容含水率检测装置。采用电容法结合反向传播(BP)算法和极限学习机(ELM)算法构建谷子含水率分析模型,温度,和体积占空比。这项工作对不同水分含量的谷子进行电容测量,温度,以及被测物质占据检测区域的比例(即,容积占空比)。在这个基础上,采用麻雀搜索算法(SSA)优化BP和ELM模型。然而,SSA可能会遇到问题,例如由于后期迭代中种群多样性的减少而陷入局部优化解决方案。因此,引入Logistic算法来优化SSA,使其更适合解决特定问题。经过比较分析,使用Logistic-SSA-ELM算法预测的模型更准确。结果表明,预测集确定系数(RP)的预测值,预测集均方根误差(RMSEP)和预测集比率性能偏差(RPDP)分别为0.7016、3.7150和1.4035。该算法具有良好的预测性能,可作为谷子水分含量检测的模型。鉴于谷子水分含量检测在采集和储存中的重要作用,研究一种无损、快速的在线实时检测方法尤为重要。所设计的差动式电容式传感器具有良好的稳定性和较高的精度,可进一步深入研究,逐步走向智慧农业、精准农业的农业发展大趋势。
    Moisture content testing of agricultural products is critical for quality control, processing efficiency and storage management. Testing foxtail millet moisture content ensures stable foxtail millet quality and helps farmers determine the best time to harvest. A differential capacitance moisture content detection device was designed based on STM32 and PCAP01 capacitance digital converter chip. The capacitance method combined with the back-propagation(BP) algorithm and the extreme learning machine(ELM) algorithm was chosen to construct an analytical model for foxtail millet moisture content, temperature, and volume duty cycle. This work performs capacitance measurements on foxtail millet with different moisture contents, temperatures, and proportions of the measured substance occupying the detection area (that is, the volumetric duty cycle). On this foundation, the sparrow search algorithm (SSA) is used to optimize the BP and ELM models. However, SSA may encounter problems such as falling into local optimization solutions due to the reduction of population diversity in the late iterations. As a consequence, Logistic algorithm is introduced to optimize SSA, making it more appropriate for solving specific problems. Upon comparative analysis, the model predicted using the Logistic-SSA-ELM algorithm was more accurate. The results indicate that the predicted values of prediction set coefficient of determination (RP), prediction set root mean square error (RMSEP) and prediction set ratio performance deviation (RPDP) were 0.7016, 3.7150 and 1.4035, respectively. This algorithm has excellent prediction performance and can be used as a model for detection of foxtail millet moisture content. In view of the important role of foxtail millet moisture content detection in acquisition and storage, it is particularly important to study a nondestructive and fast online real-time detection method. The designed capacitive sensor with differential structure has well stabilization and high accuracy, which can be further studied in depth and gradually move towards the general trend of agricultural development of smart agriculture and precision agriculture.
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  • 文章类型: Journal Article
    在本文中,我们考虑了随机采样非线性系统在存在丢包的情况下的异步估计问题。数据包丢失发生在控制输入端和测量端。首先,通过对相邻状态更新点的状态进行加权,实现异步采样系统的同步。其次,投影定理用于估计采样时的系统状态。由于建模错误和未建模的动力学,获得一个准确的动态模型是具有挑战性的。因此,提出了基于插值技术的观测推断来解决异步估计问题。此外,该算法被扩展到多传感器系统,以获得分布式融合估计器。最后,仿真实验验证了算法的有效性。
    In this paper, we consider the problem of asynchronous estimation in the presence of packet losses for the randomly sampling nonlinear system. Packet losses occur at the control input and at the measurement side. Firstly, the synchronization of the asynchronous sampling system is realized by weighting the state of the adjacent state update points. Secondly, the projection theorem is used to estimate the system state at the sampling time. Due to modeling errors and unmodeled dynamics, obtaining an accurate dynamic model is challenging. Therefore, observation inference based on interpolation techniques is proposed to solve the asynchronous estimation problem. Furthermore, the algorithm is extended to multi-sensor systems to obtain a distributed fusion estimator. Finally, simulation experiments are conducted to validate the effectiveness of the algorithm.
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  • 文章类型: Journal Article
    随着城市化进程的加快,了解和管理城市下水道网络的碳排放对于可持续的城市水循环至关重要。这篇综述研究了影响城市污水系统温室气体(GHG)排放的因素,分析水质之间的复杂影响,流体力学,以及温室气体生产和排放过程中的下水道基础设施。它揭示了温室气体排放的显著时空异质性,特别是在长期情况下,流速和温度表现出强烈的影响和相关性。鉴于存在逃逸和溶解的潜在温室气体,标准化的监控和会计方法被认为是必不可少的。先进的建模技术成为大规模碳排放预测和管理的重要工具。该综述指出,碳排放边界的传统定义和计算框架未能充分考虑下水道固有的异质性以及城市水循环过程中下水道系统内多源污染的动态变化和影响。这包括不规则的逃逸性排放,雨水系统的影响,气候变化,地理特征,下水道设计,以及食物浪费和抗生素的影响。讨论了排放管理的关键策略,重点是需要仔细考虑可能无意中增加全球排放的方法,比如通风,化学处理,和水管理实践。该审查倡导一项总体战略,包括对碳排放的整体看法,强调完善排放边界定义的重要性,新颖的会计实践,和综合管理方案,以配合水处理部门向碳中和的发展。它倡导采用跨学科,技术先进的解决方案,以减轻污染和减少碳排放,强调在未来的研究方向中整合跨尺度问题和其他环保措施的重要性。
    As urbanization accelerates, understanding and managing carbon emissions from urban sewer networks have become crucial for sustainable urban water cycles. This review examines the factors influencing greenhouse gas (GHG) emissions within urban sewage systems, analyzing the complex effects between water quality, hydrodynamics, and sewer infrastructure on GHG production and emission processes. It reveals significant spatiotemporal heterogeneity in GHG emissions, particularly under long-term scenarios where flow rates and temperatures exhibit strong impacts and correlations. Given the presence of fugitive and dissolved potential GHGs, standardized monitoring and accounting methods are deemed essential. Advanced modeling techniques emerge as crucial tools for large-scale carbon emission prediction and management. The review identifies that traditional definitions and computational frameworks for carbon emission boundaries fail to fully consider the inherent heterogeneity of sewers and the dynamic changes and impacts of multi-source pollution within the sewer system during the urban water cycle. This includes irregular fugitive emissions, the influence of stormwater systems, climate change, geographical features, sewer design, and the impacts of food waste and antibiotics. Key strategies for emission management are discussed, focusing on the need for careful consideration of approaches that might inadvertently increase global emissions, such as ventilation, chemical treatments, and water management practices. The review advocates for an overarching strategy that encompasses a holistic view of carbon emissions, stressing the importance of refined emission boundary definitions, novel accounting practices, and comprehensive management schemes in line with the water treatment sector\'s move towards carbon neutrality. It champions the adoption of interdisciplinary, technologically advanced solutions to mitigate pollution and reduce carbon emissions, emphasizing the importance of integrating cross-scale issues and other environmentally friendly measures in future research directions.
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  • 文章类型: Journal Article
    2020年3月下旬,SARS-CoV-2抵达玛瑙斯,巴西,并迅速发展为大规模流行病,崩溃了当地的卫生系统,并导致了极端的死亡率。几项关键研究报告称,到2020年10月,玛瑙斯有76%的居民受到感染(感染率为76%),这表明已经达到了保护性群体免疫。尽管如此,意外的第二波COVID-19在11月再次袭击,事实证明比第一波更大,给毫无准备的人口制造灾难.有人建议,如果第二波是由再感染驱动的,这是可能的。然而,据广泛报道,再感染的发生率很低(在Omicron出现之前),再感染往往是轻微的。这里,我们使用新的方法从死亡率数据对流行病进行建模,而不考虑再感染导致的死亡,并评估干预措施的影响以解释第二波出现的原因.该方法适合随流行病而变化的“灵活”生殖数R0(t),结果表明,该方法可以成功地从模拟数据中重建R0(t)。对于玛瑙斯来说,该方法发现,到2020年10月,第一波的AR为34%,这远低于群体免疫所需的,但与血清阳性率估计一致。这项工作得到了两应变模型的补充。利用基因组数据,该模型估计新的P.1病毒谱系的可传播性是非P.1病毒谱系的1.9倍。此外,考虑老年人高死亡率的年龄组模型变体显示出非常相似的结果.因此,这些模型为马瑙斯的两波动力学提供了合理的解释,而无需依赖大量的再感染率,到目前为止,在最近的监测工作中,只有微不足道到中等的数字被发现。
    In late March 2020, SARS-CoV-2 arrived in Manaus, Brazil, and rapidly developed into a large-scale epidemic that collapsed the local health system and resulted in extreme death rates. Several key studies reported that ∼76% of residents of Manaus were infected (attack rate AR≃76%) by October 2020, suggesting protective herd immunity had been reached. Despite this, an unexpected second wave of COVID-19 struck again in November and proved to be larger than the first, creating a catastrophe for the unprepared population. It has been suggested that this could be possible if the second wave was driven by reinfections. However, it is widely reported that reinfections were at a low rate (before the emergence of Omicron), and reinfections tend to be mild. Here, we use novel methods to model the epidemic from mortality data without considering reinfection-caused deaths and evaluate the impact of interventions to explain why the second wave appeared. The method fits a \"flexible\" reproductive number R0(t) that changes over the epidemic, and it is demonstrated that the method can successfully reconstruct R0(t) from simulated data. For Manaus, the method finds AR≃34% by October 2020 for the first wave, which is far less than required for herd immunity yet in-line with seroprevalence estimates. The work is complemented by a two-strain model. Using genomic data, the model estimates transmissibility of the new P.1 virus lineage as 1.9 times higher than that of the non-P.1. Moreover, an age class model variant that considers the high mortality rates of older adults show very similar results. These models thus provide a reasonable explanation for the two-wave dynamics in Manaus without the need to rely on large reinfection rates, which until now have only been found in negligible to moderate numbers in recent surveillance efforts.
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