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Many biological circuits produce complex outputs by exploiting one or more feedback loops. In a sequence of biochemical events, feedback would refer to a downstream element in the sequence (B in the adjacent image) affecting some upstream component (A in the adjacent image) to affect its own production or activation (output) in the future.
Current mode logic (CML), or source-coupled logic (SCL), is a digital design style used both for logic gates and for board-level digital signaling of digital data. The basic principle of CML is that current from a constant current generator is steered between two alternate paths depending on whether a logic zero or logic one is being represented.
It acts exclusively as an electrically controlled switch. The UJT is not used as a linear amplifier. It is used in free-running oscillators, synchronized or triggered oscillators, and pulse generation circuits at low to moderate frequencies (hundreds of kilohertz). It is widely used in the triggering circuits for silicon controlled rectifiers.
Types of endogenous and exogenous stimuli for molecular switches. A molecular switch is a molecule that can be switched between two or more stable or metastable states with the use of any external (exogenous) or internal (endogenous) stimuli, such as changes in pH, light, temperature, an electric current, a microenvironment, or in the presence of ions, and other ligands.
This current dependency is not supported by the characteristics shown in the diagram above a certain applied voltage. This is the saturation region, and the JFET is normally operated in this constant-current region where device current is virtually unaffected by drain-source voltage. The JFET shares this constant-current characteristic with ...
The logic was also called a current-mode circuit. [12] It was also used to make the IBM Advanced Solid Logic Technology (ASLT) circuits in the IBM 360/91. [13] [14] [15] Yourke's current switch was a differential amplifier whose input logic levels were different from the output logic levels.
Two early examples of synthetic biological circuits were published in Nature in 2000. One, by Tim Gardner, Charles Cantor, and Jim Collins working at Boston University, demonstrated a "bistable" switch in E. coli. The switch is turned on by heating the culture of bacteria and turned off by addition of IPTG.
These data are plotted as current density (j, mA/cm 2) versus potential (typically corrected for Ohmic/iR drop) (E, V). During the initial forward scan from t 0 to t 1, an increasingly oxidative (positive) potential is applied, and the anodic (positive) current increases over this time period due to the charging of the electric double layer.