Where does carrier collide?

In genetics and reproductive medicine, a carrier is a person who holds one copy of a recessive disease variant alongside one working copy, so they stay healthy themselves yet can pass the variant to a child, who is affected only if both parents transmit it. The 2015 statement Expanded Carrier Screening in Reproductive Medicine by Edwards and colleagues reviewed how couples are now tested across many conditions at once to find such hidden carriers before pregnancy. This referent is a symptom-free human host of a heritable variant, counted by its carrier frequency in a population, and it has nothing in common with a modulated radio wave, a charge inside a semiconductor, or a shipping company.[1]

Unit

One heterozygous person carrying a single recessive variant, scaled by carrier frequency in a population

Recovery means

Not applicable

Measured by

Detected by molecular carrier screening or biochemical testing that finds one copy of a variant in an unaffected person

In solid-state physics, a charge carrier is a mobile bearer of electric charge inside a material: in a semiconductor these are the conduction electrons and the positively charged holes left where an electron is missing, and current flows as these carriers drift and diffuse. Shockley's 1949 The Theory of p-n Junctions in Semiconductors and p-n Junction Transistors built the account of how electrons and holes recombine, diffuse, and cross a junction, which became the basis of the transistor. The referent is a microscopic mobile charge within a crystal, counted as a density per unit volume, and it is unrelated to a transmission wave, a person carrying a gene, or a common carrier of goods.[2]

Unit

One mobile electron or hole, scaled as a carrier density per unit volume

Recovery means

An excess carrier relaxes back toward equilibrium over a recombination lifetime once the injection stops

Measured by

Inferred from Hall-effect measurements, conductivity, and carrier-lifetime experiments

In transport and communications law, a common carrier is a firm that offers to carry goods, people, or messages for the general public on published terms, and in exchange for that public role it takes on special duties: to serve all comers without unjust discrimination, and to answer for loss of what is placed in its care. Noam's 1994 Beyond Liberalization II: The Impending Doom of Common Carriage traced the doctrine from its roots in transport to telephone and network regulation, and argued that competition was eroding it. The referent is a legal status and set of obligations attached to a business, not a radio wave, a symptom-free gene carrier, or a charge moving in a chip.[3]

Unit

One firm holding common-carrier status, defined by its public duty to serve and to answer for goods in its care

Recovery means

Not applicable

Measured by

Established in law by whether a firm holds itself out to serve the public indifferently, as decided by statute, regulator, or court