ABSTRACT
Several measures including behavioral restrictions for individuals have been taken to control the spread of COVID-19 all over the world. The aim of these measures is to prevent infected persons from contacting with susceptible persons. Since the behavioral restrictions for all citizens, such as the city-wide lockdown, are directly linked to stagnation of economic activities, the assessment of such measures is crucial. In order to evaluate the effects of behavioral restrictions, we employ the broken-link model to compare the situation of COVID-19 in Shanghai where the lockdown was implemented from March to June 2022 with it in Taiwan where a spread of COVID-19 was known to be well controlled so far. The result shows that the small link-connection probability is achieved by substantial isolation of infected person including the lockdown measures. Although the strict measures for behavioral restrictions are effective to reduce the total infected people, the daily confirmed cases follow the curve which is evaluated by the broken-link model. This result is considered as unavoidable infections for population.
ABSTRACT
We propose a new compartment model of COVID-19 spread, the broken-link model, which includes the effect from unconnected infectious links of the transmission. The traditional SIR-type epidemic models are widely used to analyze the spread status, and the models show the exponential growth of the number of infected people. However, even in the early stage of the spread, it is proven by the actual data that the exponential growth did not occur all over the world. We consider this is caused by the suppression of secondary and higher transmissions of COVID-19. We find that the proposed broken-link model quantitatively describes the mechanism of this suppression and is consistent with the actual data.
ABSTRACT
From March 1981 to March 1990, 61 patients with Stanford type B acute aortic dissection were initially treated by conservative therapy. Among these 61 patients, the dissected lumen became occluded due to thrombosis early after diagnosis in 25 patients (Group T) and remained patent in 36 patients (Group P). Twentythree patients in Group T (92%) and 22 patients in Group P (61%) were discharged without major complications related to acute aortic dissection. However, 2 patients in Group T (8%) and 14 patients in Group P (39%) required additional surgical therapy or died during hospitalization. The mean aortic diameter at the time of admission in Group T was smaller than that of Group P (38±3mm vs 43±7mm, <i>p</i><0.05). During the observation period, there was a tendency for the diameter of the dissected aorta in Group T to decrease, but to increase in Group P. Long-term survival appeared to be better in Group T than in Group P, but there was no significant difference in the overall survival curve. Large aortic diameter at the time of admission and the presence of a true thoracic aortic aneurysm were major contributing factors influencing the prognosis. A long-term follow-up study showed that the dissected lumen reduced or disappeared in 14 of 23 patients in Group T (61%) but only 2 of 16 patients in Group P (12.5%). We concluded that the patients with small dissected aortas and thrombosed dissected lumens (Group T) can recuperate only with conservative therapy. However, patients with large dissected aortas and patent dissected lumen (Group P) may require surgical therapy even in Stanford type B aortic dissection.
ABSTRACT
Congenital heart disease of partial anomalous pulmonary venous drainage of entire left lung without other cardiac anomaly was very rare. 21-year-old man, who was pointed out heart disease 6 months ago, was diagnosed as partial anomalous pulmonary venous drainage of entire left lung without other cardiac anomaly by cardiac catheterization and angiography. The patient underwent surgery through the left forth intercostal incision without cardiopulmonary bypass. The end-to-side anastomosis was made between the vertical vein and the left atrial appendage following ligation of the vertical vein near the innominate vein. Surgical treatment was satisfactory in the postoperative angiography which was shown widely patent anastomosis. He was discharged with uneventful postoperative course and returned to full activity.
