Leprosy Prevalence: the number of existing cases (new and old) from leprosy at the end of a specific year, for a given country, territory, or geographic area.
Library: an unordered collection of clones (i.e., cloned DNA from a particular organism) whose relationship to each other can be established by physical mapping. See also -- genomic library, arrayed library.
Licensing: the establishment of legal restrictions defining which individuals or (institutions) have the rights to provide services or goods (usually based on meeting minimum requirements).
Life Expectancy: the number of year of life that can be expected on average in a given population.
Life Expectancy at Birth: the average number of years that a newborn could expect to live, if he or she were to pass through life exposed to the sex- and age-specific death rates prevailing at the time of his or her birth, for a specific year, in a given country, territory, or geographic area. Technical Note: Life expectancy at birth is derived from life tables and is based on sex- and age-specific death rates. Life expectancy at birth values from the United Nations correspond to mid-year estimates, consistent with the corresponding United Nations fertility medium-variant quinquennial population projections.
Likert Response Scale: a series of responses ranging from "strongly disagree" to "strongly agree"; "excellent" to "poor"; "very satisfied" to "very dissatisfied", etc., often used to measure attitudes.
Linear Energy Transfer (LET): the energy lost by the particle of photon per micron of path depth. High LET radiations are more effective against hypoxic cells.
Linkage: the association of genes on the same chromosome. The proximity of two or more markers (e.g., genes, RFLP markers) on a chromosome; the closer the markers, the lower the probability that they will be separated during DNA repair or replication processes (binary fission in prokaryotes, mitosis or meiosis in eukaryotes), and hence the greater the probability that they will be inherited together.
Linkage Disequilibrium: where alleles occur together more often than can be accounted for by chance. Indicates that the two alleles are physically close on the DNA strand. See also -- Mendelian inheritance.
Linkage Map: a map of the relative positions of genetic loci on a chromosome, determined on the basis of how often the loci are inherited together. Distance is measured in centimorgans (cM).
Literacy Rate: the proportion of the adult population aged 15 years and over which is literate, expressed as a percentage of the corresponding population, total or for a given sex, in a given country, territory, or geographic area, at a specific point in time, usually mid-year. For statistical purposes, a person is literate who can with understanding both read and write a short simple statement on his/her everyday life. Technical Note: Literacy rate definition complies with the revised recommendation concerning the International Standardization of Educational Statistics, adopted by the United Nations Educational, Scientific and Cultural Organization (UNESCO). Literacy rate data represent mid-year estimated values.
Live Birth Weight: the complete expulsion or extraction from its mother of a product of conception, irrespective of the duration of the pregnancy, which, after such separation, breathes or shows any other evidence of life.
Localize: determination of the original position (locus) of a gene or other marker on a chromosome.
Lochia: postpartum discharge which is often blood-stained, but not foul-smelling.
Locus (pl. loci): the position on a chromosome of a gene or other chromosome marker; also, the DNA at that position. The use of locus is sometimes restricted to mean expressed DNA regions. A general term to describe a defined chromosome region. See also -- gene expression.
Longitudinal Design: a trend study, involving repeated data collection of independently selected samples from the same population over time; or: a panel study with information gathered from the same cases at two or more different times, with the sets of data linked by case.
Long-Range Restriction Mapping: restriction enzymes are proteins that cut DNA at precise locations. Restriction maps depict the chromosomal positions of restriction-enzyme cutting sites. These are used as biochemical "signposts," or markers of specific areas along the chromosomes. The map will detail the positions where the DNA molecule is cut by particular restriction enzymes.
Long-Term Care (LTC): long-term care encompasses a broad range of help with daily activities that chronically disabled individuals need for a prolonged period of time.
Loss of Heterozygosity: losses of specific regions of DNA from one copy of a given chromosome that can be distinguished from the region retained on the other chromosome.
Low Birth Weight: a birth weight of less than 2500 g.
Low Birth Weight Prevalence: the number of newborn children weighing less than 2,500 grams, as weighted at the time of birth or within the first hours of life, before significant postnatal weight loss has occurred, expressed per 1,000 live births, for a given year, in a given country, territory, or geographic area.
Lower Genital Tract Infection: includes vaginal and cervical infection.
Lower Urinary Tract: consists of the bladder, prostate gland (in men), urethra, and urinary sphincters.
LUTS: abbreviation for lower urinary tract symptoms -- a group of symptoms including 1) incontinence, 2) weak stream, 3) hesitancy, 4) urgency of urination, 5) nocturia, 6) postvoid dribbling, and 7) intermittency, an interrupted urinary stream.
Lymphocyte: a round cell with scanty cytoplasm and a diameter of 7-12 µm. the nucleus is round, sometimes indented, with chromatin arranged in coarse masses and without visible nucleoli. Lymphocytes may be actively mobile.
Lymphoid Cell: any or all cells of the lymphocytic and plasmacytic series.
Lymphokines: substances released by sensitized lymphocytes when they come into contact with the antigen to which they are sensitized; examples include transfer factor, lymphocyte-transforming activity, migration inhibition factor, and lymphotoxin.
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