scholarly journals The timing of contact restrictions and pro-active testing balances the socio-economic impact of a lockdown with the control of infections

2020 ◽  
Author(s):  
Saptarshi Bej ◽  
Olaf Wolkenhauer
Keyword(s):  
Mathematical Models ◽  
Time Dependent ◽  
Simulation Studies ◽  
Epidemiological Models ◽  
Extensive Documentation ◽  
Active Testing ◽  
Dependent Parameter ◽  
Socio Economic Impact ◽  
Parameter Values

During the SARS-CoV-2 pandemic, numerous mathematical models have been developed. Reporting artefacts and missing data about asymptomatic spreaders, imply considerable margins of uncertainty for model-based predictions. Epidemiological models can however also be used to investigate the consequences of measures to control the pandemic, reflected in changes to parameter values. We present a SIR-based, SUIR model in which the influence of testing and a reduction of contacts is studied by distinguishing 'Unidentified' and 'Identified' spreaders of infections. The model uses four ordinary differential equations and is kept deliberately simple to investigate general patterns occurring from testing and contact restrictions. The model goes beyond other efforts, by introducing time dependent parameter curves that represent different strategies in controlling the pandemic. Our analysis reveals the effect of 'pro-active' testing for the design of contact restriction measures. By pro-active testing we mean testing beyond those people who show symptoms. The simulations can explain why the timing of contract restrictions and pro-active testing is important. The model can also be used to study the consequence of different strategies to exit from lockdown. Our SUIR model is implemented in Python and is made available through a Juypter Notebooks. This an extensive documentation of the derivation and implementation of the model, as well as transparent and reproducible simulation studies. Our model should contribute to a better understanding of the role of testing and contact restrictions.

All models are wrong, but some are useful: mathematical models at the time of Covid-19

2021 ◽  
Vol 07 (01) ◽  
pp. 115-130
Author(s):  
Roberta Buiani
Keyword(s):  
Public Health ◽  
Mathematical Models ◽  
Scientific Literacy ◽  
Historical Data ◽  
Epidemiological Models ◽  
Epistemic Values ◽  
The Core ◽  
Public Health Officials

Epidemiological models have been crucial tools throughout all stages of the 2020-21 Coronavirus pandemic: using promptly available or historical data, they have studied and tried to anticipate its progression, providing valuable guidelines for public health officials, policymakers, and other medical and non-medical audiences. While useful, models are not designed to be infallible, and for this reason, they have been frequently subject to criticism. There is a discrepancy between what models do and how they are presented and perceived. Several juxtaposing factors, including current beliefs about scientific reliability, the role of quantification, and the epistemic values grounding the field, are at the core of this discrepancy. While scientific literacy may play a role in addressing this discrepancy, analyzing and becoming better aware of these factors may suggest long-term strategies to address, acknowledge, and communicate the pandemic’s inherent complexity and stochastic qualities.

CELLULAR-AUTOMATON-CONTROLLED LOGISTIC MAP: AN UNUSUAL TYPE OF NOISE

1992 ◽  
Vol 03 (03) ◽  
pp. 547-552
Author(s):  
DANIEL A. STARIOLO ◽  
CONSTANTINO TSALLIS
Keyword(s):  
Cellular Automaton ◽  
Internal Structure ◽  
Numerical Study ◽  
Logistic Map ◽  
Time Dependent ◽  
Dependent Parameter ◽  
Multiple Band ◽  
Parameter Values ◽  
Unusual Type

We present a numerical study of the logistic map dynamics with time dependent parameter values whose evolution is in turn governed by a deterministic cellular automaton. We find an unusual type of noise which presents a surprising internal structure yielding a multiple band attractor.

Pieces of Mind

2018 ◽  
Author(s):  
Carrie Figdor
Keyword(s):  
Mathematical Models ◽  
Moral Status ◽  
Entire Range ◽  
Fruit Flies ◽  
Literal Interpretation ◽  
Psychological Capacities

Many people accept that chimpanzees, dolphins, and some other animals can think and feel. But these cases are just the tip of a growing iceberg. If biologists are right, fruit flies and plants make decisions, worms and honeybees can be trained, bacteria communicate linguistically, and neurons have preferences. Just how far does cognition go? This book is the first to critically consider this question from the perspective of the entire range of new ascriptions of psychological capacities throughout biology. It is also the first to consider the role of mathematical models and other quantitative forms of evidence in prompting and supporting the new ascriptions. It defends a default literal interpretation of psychological terms across biological domains. It also considers the implications of the literal view for efforts to explain the mind’s place in nature and for traditional ways of distinguishing the superior moral status of humans relative to other living beings.

scholarly journals Structure of the full-length human Pannexin1 channel and insights into its role in pyroptosis

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Sensen Zhang ◽  
Baolei Yuan ◽  
Jordy Homing Lam ◽  
Jun Zhou ◽  
Xuan Zhou ◽  
...  
Keyword(s):  
Md Simulation ◽  
Potential Role ◽  
Md Simulations ◽  
Full Length ◽  
Inflammasome Activation ◽  
Simulation Studies ◽  
Cryo Electron Microscopy ◽  
Gating Mechanism ◽  
Atp Efflux

AbstractPannexin1 (PANX1) is a large-pore ATP efflux channel with a broad distribution, which allows the exchange of molecules and ions smaller than 1 kDa between the cytoplasm and extracellular space. In this study, we show that in human macrophages PANX1 expression is upregulated by diverse stimuli that promote pyroptosis, which is reminiscent of the previously reported lipopolysaccharide-induced upregulation of PANX1 during inflammasome activation. To further elucidate the function of PANX1, we propose the full-length human Pannexin1 (hPANX1) model through cryo-electron microscopy (cryo-EM) and molecular dynamics (MD) simulation studies, establishing hPANX1 as a homo-heptamer and revealing that both the N-termini and C-termini protrude deeply into the channel pore funnel. MD simulations also elucidate key energetic features governing the channel that lay a foundation to understand the channel gating mechanism. Structural analyses, functional characterizations, and computational studies support the current hPANX1-MD model, suggesting the potential role of hPANX1 in pyroptosis during immune responses.

The solution of an infinite set of differential-difference equations occurring in polymerization and queueing problems

1963 ◽  
Vol 59 (1) ◽  
pp. 117-124 ◽  
Author(s):  
A. Wragg
Keyword(s):  
Difference Equations ◽  
Queueing Theory ◽  
Bessel Functions ◽  
Formal Solution ◽  
Monomer Concentration ◽  
Arrival Rate ◽  
Time Dependent ◽  
Type Integral ◽  
Dependent Parameter ◽  
Infinite Set

AbstractThe time-dependent solutions of an infinite set of differential-difference equations arising from queueing theory and models of ‘living’ polymer are expressed in terms of modified Bessel functions. Explicit solutions are available for constant values of a parameter describing the arrival rate or monomer concentration; for time-dependent parameter a formal solution is obtained in terms of a function which satisfies a Volterra type integral equation of the second kind. These results are used as the basis of a numerical method of solving the infinite set of differential equations when the time-dependent parameter itself satisfies a differential equation.

scholarly journals Effect of data quality on estimates of farm infectiousness trends in the UK 2001 foot-and-mouth disease epidemic

2006 ◽  
Vol 4 (13) ◽  
pp. 235-241 ◽  
Author(s):  
Nicholas J Savill ◽  
Darren J Shaw ◽  
Rob Deardon ◽  
Michael J Tildesley ◽  
Matthew J Keeling ◽  
...  
Keyword(s):  
Mathematical Models ◽  
Data Quality ◽  
Foot And Mouth Disease ◽  
Mouth Disease ◽  
Inaccurate Data ◽  
Foot And Mouth ◽  
The Uk ◽  
Parameter Values

Most of the mathematical models that were developed to study the UK 2001 foot-and-mouth disease epidemic assumed that the infectiousness of infected premises was constant over their infectious periods. However, there is some controversy over whether this assumption is appropriate. Uncertainty about which farm infected which in 2001 means that the only method to determine if there were trends in farm infectiousness is the fitting of mechanistic mathematical models to the epidemic data. The parameter values that are estimated using this technique, however, may be influenced by missing and inaccurate data. In particular to the UK 2001 epidemic, this includes unreported infectives, inaccurate farm infection dates and unknown farm latent periods. Here, we show that such data degradation prevents successful determination of trends in farm infectiousness.

scholarly journals Endothelial cell-related autophagic pathways in Sugen/hypoxia-exposed pulmonary arterial hypertensive rats

2017 ◽  
Vol 313 (5) ◽  
pp. L899-L915 ◽  
Author(s):  
Fumiaki Kato ◽  
Seiichiro Sakao ◽  
Takao Takeuchi ◽  
Toshio Suzuki ◽  
Rintaro Nishimura ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Endothelial Cell ◽  
Vascular Remodeling ◽  
Time Dependent ◽  
Causative Role ◽  
Dependent Manner ◽  
Vascular Endothelial ◽  
Pulmonary Vascular Remodeling ◽  
Pulmonary Arterial

Pulmonary arterial hypertension (PAH) is characterized by progressive obstructive remodeling of pulmonary arteries. However, no reports have described the causative role of the autophagic pathway in pulmonary vascular endothelial cell (EC) alterations associated with PAH. This study investigated the time-dependent role of the autophagic pathway in pulmonary vascular ECs and pulmonary vascular EC kinesis in a severe PAH rat model (Sugen/hypoxia rat) and evaluated whether timely induction of the autophagic pathway by rapamycin improves PAH. Hemodynamic and histological examinations as well as flow cytometry of pulmonary vascular EC-related autophagic pathways and pulmonary vascular EC kinetics in lung cell suspensions were performed. The time-dependent and therapeutic effects of rapamycin on the autophagic pathway were also assessed. Sugen/hypoxia rats treated with the vascular endothelial growth factor receptor blocker SU5416 showed increased right ventricular systolic pressure (RVSP) and numbers of obstructive vessels due to increased pulmonary vascular remodeling. The expression of the autophagic marker LC3 in ECs also changed in a time-dependent manner, in parallel with proliferation and apoptotic markers as assessed by flow cytometry. These results suggest the presence of cross talk between pulmonary vascular remodeling and the autophagic pathway, especially in small vascular lesions. Moreover, treatment of Sugen/hypoxia rats with rapamycin after SU5416 injection activated the autophagic pathway and improved the balance between cell proliferation and apoptosis in pulmonary vascular ECs to reduce RVSP and pulmonary vascular remodeling. These results suggested that the autophagic pathway can suppress PAH progression and that rapamycin-dependent activation of the autophagic pathway could ameliorate PAH.

Second language acquisition: Theoretical and experimental issues in contemporary research

1996 ◽  
Vol 19 (4) ◽  
pp. 677-714 ◽  
Author(s):  
Samuel David Epstein ◽  
Suzanne Flynn ◽  
Gita Martohardjono
Keyword(s):  
Second Language ◽  
Second Language Acquisition ◽  
Universal Grammar ◽  
Functional Categories ◽  
L2 Acquisition ◽  
Psycholinguistic Research ◽  
Explanatory Theory ◽  
Parameter Values ◽  
Theoretical Issues

AbstractTo what extent, if any, does Universal Grammar (UG) constrain second language (L2) acquisition? This is not only an empirical question, but one which is currently investigable. In this context, L2 acquisition is emerging as an important new domain of psycholinguistic research. Three logical possibilities have been articulated regarding the role of UG in L2 acquisition: The first is the “no access” hypothesis that claims that no aspect of UG is available to the L2 learner. The second is the “partial access” hypothesis that claims that only LI instantiated principles and LI instantiated parameter-values of UG are available to the learner. The third, called the “full access” hypothesis, asserts that UG in its entirety constrains L2 acquisition.In this paper we argue that there is no compelling evidence to support either of the first two hypotheses. Moreover, we provide evidence concerning functional categories in L2 acquisition consistent with the claim that UG is fully available to the L2 learner (see also Flynn 1987; Li 1993; Martohardjono 1992; Schwartz & Sprouse 1991; Thomas 1991; White 1989). In addition, we will attempt to clarify some of currently unclear theoretical issues that arise with respect to positing UG as an explanatory theory of L2 acquisition. We will also investigate in some detail certain crucial methodological questions involved in experimentally testing the role of UG in L2 acquisition and finally, we will present a set of experimental results of our own supporting the “Full Access” hypothesis.

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