What is "transduction"

Transduction \Trans*duc"tion\, n. [L. transducere, traducere, -dictum, to lead across or over. See Traduce.] The act of conveying over. [R.]
--Entick.

"act of leading or carrying over," 1650s, from Latin transductionem/traducionem (nominative transductio) "a removal, transfer," noun of action from transducere/traducere (see traduce).

n. 1 (context biology English) The transfer of genetic material from one bacterial cell to another by a bacteriophage or plasmid 2 The process whereby a transducer converts energy from one form to another 3 (context physiology English) The conversion of a stimulus from one form to another 4 (context physics English) The conversion of energy (especially light energy) into another form, especially in a biological process such as photosynthesis or in a transducer 5 (context logic English) A form of inference involving reasoning from one specific case to another (compare induction)

1. n. (genetics) the process of transfering genetic material from one cell to another by a plasmid or bacteriophage

2. the process whereby a transducer accepts energy in one form and gives back related energy in a different form; "the transduction of acoustic waves into voltages by a microphone"

Transduction (trans- + -duc- + -tion, "leading through or across") can refer to:

• Signal transduction, any process by which a biological cell converts one kind of signal or stimulus into another
  • Olfactory transduction
  • Sugar signal transduction
• Transduction (biophysics), the conveyance of energy from a donor electron to a receptor electron, during which the class of energy changes
• Transduction (genetics), the transfer of viral, bacterial, or both bacterial and viral DNA from one cell to another using a bacteriophage vector
  • Tbx18 transduction, a cardiac therapy method
• Transduction (machine learning), the process of directly drawing conclusions about new data from previous data, without constructing a model
• Transduction (physiology), the transportation of stimuli to the nervous system
• Transduction (psychology), reasoning from specific cases to general cases, typically employed by children during their development
• A process by which a transducer converts one type of energy to another

In physiology, sensory transduction is the conversion of a sensory stimulus from one form to another.

Transduction in the nervous system typically refers to stimulus alerting events wherein a physical stimulus is converted into an action potential, which is transmitted along axons towards the central nervous system where it is integrated.

A receptor cell converts the energy in a stimulus into a change in the electrical potential across its membrane. It causes the depolarization of the membrane to allow the action potential to be transduced to the brain for integration.

Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector. An example is the viral transfer of DNA from one bacterium to another. Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA (which occurs in conjugation), and it is DNase resistant ( transformation is susceptible to DNase). Transduction is a common tool used by molecular biologists to stably introduce a foreign gene into a host cell's genome.

When bacteriophages (viruses that infect bacteria) infect a bacterial cell, their normal mode of reproduction is to harness the replicational, transcriptional, and translation machinery of the host bacterial cell to make numerous virions, or complete viral particles, including the viral DNA or RNA and the protein coat.

In biophysics, transduction is the conveyance of energy from one electron (a donor) to another (a receptor), at the same time that the class of energy changes.

Photonic energy, the kinetic energy of a photon, may follow the following paths:

• be released again as a photon of less energy;
• be transferred to a recipient with no change in class;
• be dissipated as heat; or
• be transduced

In photosynthesis, when the electrons of the " chlorophyll pair" receive the photon energy from the "collecting" associated pigments, the photonic energy is "destined" to link one molecule of phosphate to one of NAD. The resulting NADP in turn will use the stored energy in the generation of ATP, which is the end point of the light-induced photosynthetic process. [This is quite wrong: NADP is reduced (electrons are added) to NADPH in the light reactions of linear electron transport. No ATP involved directly. Phosphate is "linked" to ADP, forming ATP, but this does not involve NADP(H), it involves the proton gradient (and ATP synthase) generated by photosynthetic electron transport processes.] This means that the photon's energy ends up its circuit by being transduced to an electron that takes part in the formation of a molecular link of energy-rich phosphate.

In the pathway of this end-point transduction, the energy is transferred along a number of molecules ( cytochromes), in a downward way so that energy is partially dissipated at each step. The liberated heat energy serves the homeostasis of the plant, and at the end of the chain the remaining energy is perhaps exactly the one that is needed to build NADP.

This process is committed; i.e. there is no return path. Homeostasis, theoretically, might save the day only at the beginning: before the luminic energy transferred to the "chlorophyl pair" is conveyed to the first element of the cytochrome chain, there is a gap in the process when the energy is carried as a series of excitons. These are now called resonant-energy-transferring molecules of the chlorophyll class, which transfer what is considered electromagnetic energy, from one to its neighbor with no participation of electrons nor enzymes. At this stage, if the first pigment has received an excess of light, the "exciton" perhaps might dissipate the energy as heat.

In logic, statistical inference, and supervised learning, transduction or transductive inference is reasoning from observed, specific (training) cases to specific (test) cases. In contrast, induction is reasoning from observed training cases to general rules, which are then applied to the test cases. The distinction is most interesting in cases where the predictions of the transductive model are not achievable by any inductive model. Note that this is caused by transductive inference on different test sets producing mutually inconsistent predictions.

Transduction was introduced by Vladimir Vapnik in the 1990s, motivated by his view that transduction is preferable to induction since, according to him, induction requires solving a more general problem (inferring a function) before solving a more specific problem (computing outputs for new cases): "When solving a problem of interest, do not solve a more general problem as an intermediate step. Try to get the answer that you really need but not a more general one." A similar observation had been made earlier by Bertrand Russell: "we shall reach the conclusion that Socrates is mortal with a greater approach to certainty if we make our argument purely inductive than if we go by way of 'all men are mortal' and then use deduction" (Russell 1912, chap VII).

An example of learning which is not inductive would be in the case of binary classification, where the inputs tend to cluster in two groups. A large set of test inputs may help in finding the clusters, thus providing useful information about the classification labels. The same predictions would not be obtainable from a model which induces a function based only on the training cases. Some people may call this an example of the closely related semi-supervised learning, since Vapnik's motivation is quite different. An example of an algorithm in this category is the Transductive Support Vector Machine (TSVM).

A third possible motivation which leads to transduction arises through the need to approximate. If exact inference is computationally prohibitive, one may at least try to make sure that the approximations are good at the test inputs. In this case, the test inputs could come from an arbitrary distribution (not necessarily related to the distribution of the training inputs), which wouldn't be allowed in semi-supervised learning. An example of an algorithm falling in this category is the Bayesian Committee Machine (BCM).

Transduction in general is the transportation or transformation of something from one form, place, or concept to another. In psychology, transduction refers to reasoning from specific cases to general cases, typically employed by children during their development. The word has many specialized definitions in varying fields. Furthermore, transduction is defined as what takes place when many sensors in the body convert physical signals from the environment into encoded neural signals sent to the central nervous system.