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lead optimization

(lēd) The synthetic refinement of a candidate drug from its crude or original state into an agent that is safer, more useful, or more marketable.

lead poisoning

SEE: under poisoning.

lead poisoning, chronic

SEE: under poisoning.


(lēf′lĕt) The part of a valve designed to open in the direction of flow and close to prevent backflow. Its base is typically attached to a larger structure by a fixed stalk; its unattached end moves.

flail mitral valve l. A mitral valve leaflet that billows into the left atrium during ventricular systole allowing blood to regurgitate (flow backward) into the atrium.


To escape or be released passively from a cell, tissue, or organ.

leakage current

In electrosurgery current that flows toward a ground along a path that the surgeon did not intend.


(lēn) Without excess fat. By USDA standards it means that a meat or poultry product contains less than 10 g of fat, 4.5 g of saturated fat and 95 mg of cholesterol per serving.

Leapfrog Group

An initiative driven by Fortune 500 companies and other large private and public health care purchasers working to initiate breakthrough improvements in the safety, quality, and affordability of health care through technology.

learned nonuse

Behavior sometimes observed in patients with hemiparesis in whom functional use of the paralyzed arm is avoided after unsuccessful attempts to use it. This phenomenon may represent a special application of learned helplessness.


(lĕrn′ing) Knowledge or skill acquired by instruction, study, experience, or practice.

action l. Learning through direct participation in a task, followed by analysis of one’s performance.

PATIENT CARE: It is used to improve work processes within organizational units or to address issues of patient care across organizational lines. Team members are chosen for their technical, organizational, or managerial skills and knowledge.

asynchronous l. Learning in which students access course material and engage with instructors and other students in distant places or at different times. Techniques in asynchronous learning include on-line chats, threaded discussions, or self-directed learning modules. Before the world wide web, asynchronous learning was called correspondence education.

blended l. Academic instruction that combines computer- or web-aided instruction with direct student-teacher contact.

deep l. The use of neural networks to analyze large quantities of real data and identify in them (without explicit preprogrammed instructions) crucial features that may not otherwise be apparent.


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