scholarly journals Dynamics of SEIR model with delay effects - latent period and recovery period

2021 ◽  
Vol 1913 (1) ◽  
pp. 012140
Author(s):  
S Raut ◽  
S Janardhan
Keyword(s):  
Latent Period ◽  
Recovery Period ◽  
Seir Model ◽  
Delay Effects

scholarly journals Analytical Solution of a New SEIR Model Based on Latent Period-Infectious Period Chronological Order

2021 ◽  
Author(s):  
Xiaoping Liu
Keyword(s):  
Analytical Solution ◽  
Latent Period ◽  
Infectious Period ◽  
Chronological Order ◽  
Underlying Assumption ◽  
Seir Model ◽  
Model Based ◽  
Exposed Individual ◽  
Line Passing ◽  
Model Equations

The Susceptible-Infectious-Recovered (SIR) and SIR derived epidemic models have been commonly used to analyze the spread of infectious diseases. The underlying assumption in these models, such as Susceptible-Exposed-Infectious-Recovered (SEIR) model, is that the change in variables E, I or R at time t is dependent on a fraction of E and I at time t. This means that after exposed on a day, this individual may become contagious or even recover on the same day. However, the real situation is different: an exposed individual will become infectious after a latent period (l) and then recover after an infectious period (i). In this study, we proposed a new SEIR model based on the latent period-infectious period chronological order (Liu X., Results Phys. 2021; 20:103712). An analytical solution to equations of this new SEIR model was derived. From this new SEIR model, we obtained a propagated curve of infectious cases under conditions l>i. Similar propagated epidemic curves were reported in literature. However, the conventional SEIR model failed to simulate the propagated epidemic curves under the same conditions. For l<i, the new SEIR models generated bell-shaped curves for infectious cases, and the curve is near symmetrical to the vertical line passing the curve peak. This characteristic can be found in many epidemic curves of daily COVID-19 cases reported from different countries. However, the curve generated from the conventional SEIR model is a right-skewed bell-shaped curve. An example for applying the analytical solution of the new SEIR model equations to simulate the reported daily COVID-19 cases was also given in this paper.

Edge-based SEIR dynamics with recovery rate in latent period on complex networks

2020 ◽  
Vol 31 (04) ◽  
pp. 2050057
Author(s):  
Rong Zhou ◽  
Qingchu Wu
Keyword(s):  
Latent Period ◽  
Recovery Rate ◽  
Stochastic Simulations ◽  
Epidemic Threshold ◽  
Seir Model ◽  
Scale Free ◽  
Epidemic Size ◽  
Final Epidemic Size ◽  
Full Analysis ◽  
Edge Based

Disease and information spreading on social and information networks have often been described by ordinary differential equations. A recent research by the authors [Y. Wang et al., Commun. Nonlinear Sci. Numer. Simulat. 45, 35 (2017).] presented an analysis of susceptible-exposed-infected-recovered (SEIR) model with and without infectious force in latent period. We present a full analysis in the more general scenario where the exposed nodes can get vaccinated or recovered. The basic reproduction number and the final epidemic size are theoretically derived. Compared to the standard SEIR model without recovery rate in latent period, our results reveal that both the recovery rate in latent period and the length of latent period can increase the epidemic threshold and inhibit the epidemic outbreak. In addition, the model predictions agree well with the continuous-time stochastic simulations in Erdős–Rényi random graphs and scale-free configuration networks.

scholarly journals SEIR Transmission dynamics model of 2019 nCoV coronavirus with considering the weak infectious ability and changes in latency duration

2020 ◽  
Author(s):  
Shi Pengpeng ◽  
Cao Shengli ◽  
Feng Peihua
Keyword(s):  
Latent Period ◽  
Incubation Period ◽  
Dynamics Model ◽  
Occurrence Time ◽  
Integration Algorithm ◽  
Seir Model ◽  
Intervention Measures ◽  
The Government ◽  
Latency Duration ◽  
Transmission Ability

ABSTRACTPneumonia patients of 2019-ncov in latent period are not easy to be effectively quarantined, but there is evidence that they have strong infectious ability. Here, the infectious ability of patients during the latent period is slightly less than that of the infected patients was assumed. We established a new SEIR propagation dynamics model, that considered the weak transmission ability of the incubation period, the variation of the incubation period length, and the government intervention measures to track and isolate comprehensively. Based on the raw epidemic data of China from January 23, 2020 to February 10, 2020, the dynamic parameters of the new present SEIR model are fitted. Through the Euler integration algorithm to solve the model, the effect of infectious ability of incubation patients on the theoretical estimation of the present SEIR model was analyzed, and the occurrence time of peak number in China was predicted.

The Clinical, Roentgenological and Morphological Effects of an Acute Exposure of Phosgene on the Lungs of Dogs

1971 ◽  
Vol 29 ◽  
pp. 236-237
Author(s):  
R. F. Bils ◽  
W. F. Diller ◽  
F. Huth
Keyword(s):  
Latent Period ◽  
Chemical Industry ◽  
Toxic Substance ◽  
Lung Edema ◽  
X Rays ◽  
Beagle Dogs ◽  
Male And Female ◽  
Morphological Alterations ◽  
Before And After ◽  
Electron Microscopes

Phosgene still plays an important role as a toxic substance in the chemical industry. Thiess (1968) recently reported observations on numerous cases of phosgene poisoning. A serious difficulty in the clinical handling of phosgene poisoning cases is a relatively long latent period, up to 12 hours, with no obvious signs of severity. At about 12 hours heavy lung edema appears suddenly, however changes can be seen in routine X-rays taken after only a few hours' exposure (Diller et al., 1969). This study was undertaken to correlate these early changes seen by the roengenologist with morphological alterations in the lungs seen in the'light and electron microscopes.Forty-two adult male and female Beagle dogs were selected for these exposure experiments. Treated animals were exposed to 94.5-107-5 ppm phosgene for 10 min. in a 15 m3 chamber. Roentgenograms were made of the thorax of each animal before and after exposure, up to 24 hrs.

Ultrastructure of mesotheliomas

1984 ◽  
Vol 42 ◽  
pp. 98-101
Author(s):  
Irving Dardick
Keyword(s):  
Electron Microscopy ◽  
Latent Period ◽  
Spindle Cell ◽  
Spindle Cell Sarcoma ◽  
Metastatic Adenocarcinoma ◽  
Cell Sarcoma ◽  
Cytological Features ◽  
Industrial Use ◽  
Degree Of Differentiation

With the extensive industrial use of asbestos in this century and the long latent period (20-50 years) between exposure and tumor presentation, the incidence of malignant mesothelioma is now increasing. Thus, surgical pathologists are more frequently faced with the dilemma of differentiating mesothelioma from metastatic adenocarcinoma and spindle-cell sarcoma involving serosal surfaces. Electron microscopy is amodality useful in clarifying this problem.In utilizing ultrastructural features in the diagnosis of mesothelioma, it is essential to appreciate that the classification of this tumor reflects a variety of morphologic forms of differing biologic behavior (Table 1). Furthermore, with the variable histology and degree of differentiation in mesotheliomas it might be expected that the ultrastructure of such tumors also reflects a range of cytological features. Such is the case.

The Effect of Exercise and Distraction on Blood Pressure Recovery Following an Anger-Provoking Stressor in Normotensive Young Adults

2015 ◽  
Vol 29 (2) ◽  
pp. 45-54 ◽  
Author(s):  
Faye S. Routledge ◽  
Judith A. McFetridge-Durdle ◽  
Marilyn Macdonald ◽  
Lynn Breau ◽  
Tavis Campbell
Keyword(s):  
Blood Pressure ◽  
Cardiovascular Health ◽  
Exercise Intervention ◽  
Recovery Period ◽  
Intervention Group ◽  
Exercise Group ◽  
State Anger ◽  
Increased Risk ◽  
Anger Reactivity ◽  
Quiet Sitting

Ruminating about a prior anger provoking event is found to elevate blood pressure (BP) and delay BP recovery. Delayed BP recovery may be associated with increased risk of hypertension. Interventions that improve BP recovery may be beneficial for cardiovascular health. The purposes of this study were to evaluate the influence of rumination and anger on BP reactivity and recovery, to compare the effect of an exercise intervention or distraction intervention on BP recovery and to explore if exercise improved BP recovery by distracting participants from stressor-related rumination and anger. Healthy, normotensive participants (n = 79, mean age 22.2 ± 4.0 years) underwent an anger-recall interview stressor task, 3 min of exercise (walking), distraction (reading) or no-intervention (quiet sitting) and a 15 min recovery period. State anger reactivity was associated with Δ diastolic (D) BP reactivity and approached significance with Δ systolic (S) BP reactivity. Trait rumination was associated with greater SBP during recovery. Δ SBP recovery did not differ between the exercise, distraction and no-intervention groups. Although there were no differences in Δ DBP recovery between the exercise and no-intervention groups, distraction improved Δ DBP recovery compared to the exercise intervention but not the no-intervention. The proportion of anger-related thoughts (state rumination) in the exercise group did not differ from the distraction or no-intervention groups. However, a smaller proportion of participants in the distraction intervention reported an anger-related thought during recovery compared to the no-intervention group with 76% of their thoughts relating to the provided distraction. Overall, post-stressor exercise was not found to improve BP recovery while reading was effective at distracting individuals from angry thoughts (state rumination) but had no effect on BP compared to no-intervention.

RELATIVE CONTRIBUTIONS OF FIBROSIS AND CONNEXIN CHANGES TOTHE ATRIAL FIBRILLATION SUBSTRATE DURING THE DEVELOPMENT AND REVERSAL OF CONGESTIVEHEART FAILURE

2008 ◽  
Vol 31 (4) ◽  
pp. 5
Author(s):  
Brett Burstein ◽  
Kunihiro Nishida ◽  
Philippe Comtois ◽  
Louis Villenuve ◽  
Yung-Hsin Yeh ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Potential Model ◽  
Diastolic Pressure ◽  
Recovery Period ◽  
Left Ventricular ◽  
Muscle Bundle ◽  
Protein Ratio ◽  
Conduction Disturbances ◽  
Conduction Abnormalities ◽  
Mrna And Protein Expression

Background: Connexin alterations occur in various atrial fibrillation (AF) paradigms, but their functional significance remains unclear. No data are available regarding the effects of CHF on atrial connexin expression and phosphorylation. We therefore analyzed connexin changes and their contribution to the AF substrate during the development and reversal ofCHF. Methods and Results: Dogs were allocated to three groups: CHF induced by 2-week ventricular tachypacing (CHF, n=15); CHF dogs allowed to recover for 4 weeks after 2-week tachypacing (REC, n=15) and non-paced shams (CTL, n=11). Left ventricular end-diastolic pressure increased with CHF (14.5±1.0*** vs.3.7±0.7, ***P < 0.001 vs. CTL) and normalized upon CHF recovery (5.1±1.0^†††, ^††† P < 0.001 vs. CHF). Real-time PCR and Western-blot analyses revealed connexin43 (Cx43) and connexin40 (Cx40) mRNA and protein expression to be unchanged by CHF and REC. However, CHF caused Cx43 dephosphorylation(by ~73%***) and increased Cx40/Cx43 protein ratio (by ~35%***), with both alterations completely reversing in REC. Immunofluorescent confocal microscopy confirmed connexin protein trends, with a reduction in phosphorylated Cx43 (by ~68%*** in CHF) that returned to control in REC. CHF caused conduction abnormalities (phasedelay-range and heterogeneity index, both P < 0.01) and burst pacing-induced AF prolongation (CTL 22±7s, CHF 1100±171s***, REC 884±220s***) which persisted in the recovery period, along with residual fibrosis (CTL 3.6±0.7%, CHF 14.7±1.5%***, REC13.3±2.3%***). Fibrosis physically interrupted muscle bundle continuity and anionically-based action potential model of canine atrium showed that fibrosiswas able to account for the observed conduction abnormalities. Conclusions: CHF causes connexin-dephosphorylation and Cx40/Cx43ratio increases. With CHF reversal, atrial connexin alterations recover completely, but tissue fibrosis, conduction abnormalities and a substrate forAF remain with fibrosis accounting for conduction abnormalities. Thus, althougha trial connexin changes occur with CHF, they are not essential for conduction disturbances and AF promotion, which appear rather to be related primarily tofibrotic interruption of muscle-bundle continuity.

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