| OEF | oil immersion field; oxygen extraction fraction |
|---|---|
| PPF | pellagra preventive factor; phagocytosis promoting factor; phosphonoformate; plasma protein fraction... |
| REF | ejection fraction at rest; referred; refused; renal erythropoietic factor |
| REFI | regional ejection fraction image |
| RF | radial fiber; radio frequency; receptive field; regurgitant fraction; Reitland-Franklin [unit]; rela... |
| liquid human serum | The pool of fluids separated from blood withdrawn from human subjects and allowed to clot in the absence of any anticoagulant; not more than 10 separate donations are pooled; the contributions from donors of A, O, and either B or AB groups are represented in approximately the ratio 9:9:2. (05 Mar 2000) |
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