Purpose The purpose of this study is to quantify the motion dynamics of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods Three physical models of Newton's and Stokes's laws with(out) air resistance in the calm air are used to determine the falling time and velocity regimes of SARS-CoV-2 with(out) a respiratory water droplet of 1 to 2000 micrometers (µm) in diameter of an infected person of 0.5 to 2.6 m in height. Results The horizontal distance travelled by SARS-CoV-2 in free fall from 1.7 m was 0.88 m due to breathing or talking and 2.94 m due to sneezing or coughing. According to Newton's laws of motion with air resistance, its falling velocity and time from 1.7 m were estimated at 3.95 × 10 −2 m s −1 and 43 s, respectively. Large droplets > 100 µm reached the ground from 1.7 m in less than 1.6 s, while the droplets ≥ 30 µm fell within 4.42 s regardless of the human height. Based on Stokes's law, the falling time of the droplets encapsulating SARS-CoV-2 ranged from 4.26 × 10 −3 to 8.83 × 10 4 s as a function of the droplet size and height. Conclusion The spread dynamics of the COVID-19 pandemic is closely coupled to the falling dynamics of SARS-CoV-2 for which Newton's and Stokes's laws appeared to be applicable mostly to the respiratory droplet size ≥ 237.5 µm and ≤ 237.5 µm, respectively. An approach still remains to be desired so as to better quantify the motion of the nano-scale objects.
A simplified model has been devised to estimate the falling dynamics of severe acute respiratory syndrome corona-virus 2 (SARS-CoV-2)-laden droplets in an indoor environment. Our estimations were compared to existing literature data. The spread of SARS-CoV-2 is closely coupled to its falling dynamics as a function of respiratory droplet diameter (1 to 2000 μm) of an infected person and droplet evaporation. The falling time of SARS-CoV-2 with a respiratory droplet diameter of about 300 μm from a height of 1.7 m remained almost the same among the Newtonian lift equation, Stokes’s law, and our simplified model derived from them so as to account for its evaporation. The evaporative demand peaked at midday which was ten times that at midnight. The evaporating droplets
6 μm lost their water content rapidly, making their lifetimes in the air shorter than their falling times. The droplets
6 μm were able to evaporate completely and remained in the air for about 5 min as droplet nuclei with SARS-CoV-2.
Background?The absence of suitable adjacent recipient vessels for microvascular anastomosis due to trauma poses a major challenge to the reconstructive surgeon. The anterior and posterior tibial vessels of the contralateral leg are the two other alternatives for use as recipient vessels for microvascular anastomosis. This method is known as the cross-leg free flap.
Methods?Twenty-seven patients (20 males, 7 females) underwent cross-leg free flap operations due to absence of a suitable adjacent recipient vessel between 2007 and 2015. The mean soft tissue defect dimension was 12???11 cm (smallest: 6???7 cm; largest: 20 ?14 cm). Gustilo type 3B tibia fractures were present in 19 patients, but no fractures were present in the other 8. Six different flaps were used: 14 anterolateral thigh flaps, 6 latissimus dorsi flaps, 3 gracilis muscle flaps, 2 vastus lateralis musculocutaneous flaps, 1 tensor fascia latae flap, and 1 deep inferior epigastric perforator flap.
Results?Two anterolateral thigh flaps failed, while the rest of the flaps survived completely. There were no donor-site complications.
Conclusion?We think that the cross-leg free flap method can be safely and successfully used with all flap types in complex lower extremity injuries in which the adjacent recipient vessel option is unavailable.
Osteomas are located mostly in the mandible followed by paranasal sinuses such as frontal sinuses, ethmoid air cells, maxillary sinuses and rarely based on nazal cavitiy or turbinate. The osteoma located on outside of nazal bone is extremely rare. The authors report an unusual patient of nasal bone osteoma associated with aesthetic problem on nasal dorsum. Outer side of nasal bone osteoma in large diameter causes aesthetic problems. The authors believe that open rhinoplasty approach is successful in this type of patients.
BACKGROUND: Classifications of nasal fracture are based on clinical findings or radiological findings. The classification systems of nasal fracture usually determine the type of nasal fracture. It is important that a classification gives information about treatment modality and prognosis rather than determining the type of fracture. The objective of this study was to show the effect of the new topographic classification on determining the parameters of prognosis and deciding on treatment modality of the nasal fracture.
METHODS:We reviewed patients with nasal fracture that was referred from emergency department between December 2018 and September 2020. The views of lateral nasal radiography, the facial view of computed tomography (CT), and/or the views of three-dimensional CT were examined to analyze 120 patients with nasal bone fractures. The length of the nasal bone from the top to the base was divided into equal three levels by two lines perpendicular to the length of the nose. The location of fracture was determined as level I, II, and III, respectively, from caudal part to cranial part of the nasal bone. The demographic features of patients, the side of the fracture, the pattern of fracture, accompanying fractures, and the treatment modality were noted.
RESULTS:The frequencies of location of nasal fractures were 44%, 28%, and 27% at level I, level II, and level III, respectively, in 120 cases. It was an expected result that the frequency of fractures was low in parts with the thick bone. Considering the rates of being bilateral or unilateral, it was found that the frequency of unilateral was higher in group of level I, where the thickness of nasal bone was thin, but it was less in group of level III (p<0.05). Non-depressed/minimal-depressed pattern of fracture in group of level I accounted for 92.6% which was the highest frequency (p<0.05). Depressed/elevated fracture patterns were more common in group of level II (p<0.05). Comminuted pattern was mostly observed in group of level III. The rate of accompanying fractures and the applied treatment modality was consistent with anatomic feature of fracture's level.
CONCLUSION:We believe that the new topographic classification evaluates the parameters of clinical prognosis such as accompanying fracture, site of fracture and pattern of fracture, and also requirement of closed or open reduction better than other classifications.
We clarified the LTA perforator flap nomenclature and defined its pedicle course and anastomosing patterns; furthermore, we demonstrated that the LTA perforator did not anastomose with its counterpart because of its unidirectional, oblique, and craniocaudal course. The LTA perforator flap was found to be a good model comprising multiple vascular territories and exhibiting continuous necrosis.
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