Effusion

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effusion

1. the flow of a gas through a small aperture under pressure, esp when the density is such that the mean distance between molecules is large compared to the diameter of the aperture
2. Med
a. the escape of blood or other fluid into a body cavity or tissue
b. the fluid that has escaped

Effusion

 

the slow leakage of gas through a small aperture. Two cases of effusion are distinguished. In the first case, the diameter of the opening is small compared with the mean free path of the molecules (the pressure in the vessel is very low). In such a case, molecular effusion occurs in which collisions between molecules play no part, and the overall volume of gas escaping per unit time is Effusion, where S is the area of the aperture, μ is the molecular mass of the gas, R is the universal gas constant, T is the absolute temperature of the gas, and p1 and p2 are the gas pressures on the two sides of the aperture. The effusion method of measuring very low pressures (about 10–3–10–4 mm Hg) is based on this case.

In the second case, where the gas pressure is so high that the mean free path is smaller than the diameter of the aperture, the leakage of gas obeys the laws of hydrodynamics. The molecules escape from the aperture in the form of a jet, and the volume of gas discharged per unit time is inversely proportional to the square root of the density of the gas. This law underlies a method of determining the density of gases from the time of their discharge through small apertures (0.10–0.01 mm). However, if the pressure within the vessel is considerably greater than the external pressure, the amount of gas escaping is proportional to the pressure in the vessel.


Effusion

 

the process of lava (magma) pouring out onto the earth’s surface. When the lava cools, effusive rocks are formed, bedded in the form of lava flows and lava sheets. Effusion, one of the manifestations of volcanic activity, is usually accompanied by an explosion, with discharges of small fragments (volcanic ash, sand, or tuff) or large chunks (volcanic bombs and slags). Viscous acidic lava sometimes will not flow, but rather is extended, forming volcanic domes.

effusion

[e′fyü·zhən]
(medicine)
A pouring out of any fluid into a body cavity or tissue.
(physical chemistry)
The movement of a gas through an opening which is small as compared with the average distance which the gas molecules travel between collisions.
(science and technology)
The act or process of leaking or pouring out.
Any material that is effused.
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An unusual presentation of anti-Jo-1 syndrome, mimicking lung metastases, with massive pleural and pericardial effusions.
In areas where Lyme disease is common, physicians should always consider whether a spontaneous knee effusion might be caused by the disease and test accordingly.
Imaging revealed cardiomegaly (Figure 2a), a large pericardial effusion and pneumatosis intestinalis of the ascending colon (Figure 2b), and global cardiomyopathy with an ejection fraction of 25% to 30% (Figures 2c, 2d).
7) Reactive mesothelial cells are commonly found in canine pericardial effusions and often cytologically closely resemble neoplastic cells.
The most common causes of pleural effusions are congestive heart failure, pneumonia, liver disease, end-stage renal disease and cancer.
Neoplastic effusions: histological evidence of a malignant effusion or a tumour, in the absence of other causes of pleural effusion.
Drugs associated with pleural effusions Rare * Amiodarone * Phenytoin * Methotrexate Very rare * Carbamazepine * Cyclophosphamide * Penicillamine
Contrast-enhanced computed tomography (CT) of the chest confirmed bilateral pleural effusions with consolidation of the right lower zone of the lung, but no pulmonary nodules, mediastinal or hilar lymphadenopathy (Fig.
Diagnostic flexible fiberoptic pleuroscopy in suspected malignant pleural effusions.
Pericardial Tamponade and Large Pericardial Effusions Causal Factors and Efficacy of Percutaneous Catheter Drainage in 50 Patients.
CRF raised serum creatinine, pulmonary edema, pleural effusion, ascites, raised ALTs.