ABSTRACT
Background Subways are typical congregate settings and may facilitate aerosol transmission of viruses. However, quantified transmission probability estimates are lacking. Purpose To model spread and diffusion of respiratory aerosols in subways by simulation and calculation of infection probabilities. Methods The internal environment of carriages of Shanghai Metro Line 10 was used to establish a study scene. The movement of tiny particles was simulated using the turbulent model. Trend analysis of infection probabilities and viral quantum doses was conducted in a closed subway carriage scene by a quantum emission-infection probability model. Results Under a typical twelve-vent air conditioning configuration, respiratory droplet aerosols within a subway carriage dispersed rapidly throughout various regions due to airflow, with limited short-term diffusion to other carriages. Concurrently, owing to the uncertainty of airflow patterns, the airflow might circulate and converge within carriages, causing delayed outward dispersion or hindered dispersion of droplet aerosols upon entry into these zones. Passengers boarding the carriage could exacerbate the formation of these zones. When the air conditioning system functioned adequately (air exchange rate=23.21 h−1), the probability of a virus carrier transmitting the virus to other passengers within the same carriage via aerosol transmission was approximately 3.8%. However, in the event of air conditioning system failure (air exchange rate=0.5 h−1), this probability escalated dramatically to 30%. Furthermore, a super-spreader (with virus spreading exceeding 90% of the average) elevated the infection probability to 14.9%. Additionally, due to the complexity of turbulence within the carriage, if local diffusion occurred in 1/2 zones of a carriage, the anticipated infection probability would increase to 8.9%, or during the morning or evening rush hours leading to elevated aerosol concentrations, the infection probability would rise to 4.7%. The subway transmission probability for common coronaviruses diminished to as low as 0.9%. Conclusion Combined computational fluid dynamics and infection probability analysis reveals that in the prevalent twelve-vent air conditioning configurations, despite being a major transportation hub with substantial spatial-temporal overlap, the internal space of subway carriages exhibits a certain level of resistance to virus aerosol transmission owing to built-in ventilation capabilities. However, turbulence and passenger positioning may lead to localized hovering of droplet aerosols, thereby increase the risk of virus transmission. Furthermore, super-spreaders, poor operational status of built-in air conditioning system, and high passenger volume at morning or evening peak hours exert profound effects on virus transmission and infection probability.
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Novel composite meshes routinely used in laparoscopic hernia repair reportedly lead to fewer and less dense visceral adhesions and may provide a viable alternative in thoracic surgery as well. A total of 15 adult domestic pigs underwent full thickness chest wall resection and reconstruction with Parietene [polypropylene composite; PTE, n = 5], Parietex [polyester composite; PTX, n = 5] or Bard [purely polypropylene, n = 5] mesh. After an observation period of 90 days all animals were sacrificed, intrathoracic adhesions classified via thoracoscopy [VATS], meshes explanted and peak peal strength required for lung/mesh separation recorded. Adhesions assessed through VATS-exploration were strongest in the PTX-Group while PTE and BM showed comparable results. Tensiometric analyses of peak peal strength confirmed lower values in BM than for PTE and PTX. Both composite materials showed good overall bioincorporation with post-surgical perigraft-fibrosis being strongest in BM. We consider composite grafts a suitable alternative for chest wall reconstruction. They are characterized by good overall biointegration and limited perigraft-fibrosis, thus potentially facilitating redo-procedures, even though a hydrophilic coating per se does not appear to prevent intrathoracic adhesion formation
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10.3969/j.issn.2095-4344.2013.24.024
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Objective To summarize the clinical experience of treatment of recurred urinary stone.Methods The patients who needed to be treated again from 1998 to 2002 were reviewed.Results Patients with recurred urinary stone were differentiated by symptom,the causation of recurred stone and operation.Conclusion The pointed step must be adopted based on the clinical character of recurred urinary stone.Preventing against recurred and choosing appropriate method can improve the treatment effect.
ABSTRACT
Objective To study the curative effect of transurethral incision for male urethral stricture or atresia. Methods A retrospective) review was made on 55 male patients with urethral stricture or atresia treated by transurethral incision. Results The success rate of the operation on one session was 90.9% (50/55), while the remaining 5 patients were cured by two times of operations.Forty-seven patients were followed for 6~12 months (mean,10 months).Urethral dilatation was performed for once within 1 week after the remorval of catheter in 10 patients,for 3~5 times within 3 months after operation in 21 patients,and after the third postoperative month in 16 patients. Conclusions Transurethral incision for male urethral stricture or atresia is effective.