NOR Logic Gates Research Articles

Mix-and-Match Riboswitches

Riboswitches are noncoding RNA elements found in the 5'-untranslated region of messenger RNA (mRNA) that mediate gene expression in a cis fashion in the absence of protein. This common regulatory strategy in bacteria is achieved through the interplay of two distinct domains: an aptamer domain responsible for sensing intracellular concentrations of a specific metabolite and a domain containing a secondary structural switch directly controlling expression. In a recent study, riboswitches have been discovered that are capable of regulating transcription by using an RNA architecture mimicking a Boolean NOR logic gate. Tandem arrangement of elements that recognize S-adenosylmethionine and coenzyme B12 yields an mRNA that is only expressed when both metabolites are in low concentration in the cell.

New imidazolium systems bearing two pyrene groups as fluorescent chemosensors for anions and anion induced logic gates

Two new imidazolium systems bearing two pyrene groups have been synthesized and the binding properties of these hosts were examined via fluorescent changes. The fluorescent changes of host 2 upon the addition of anions were also utilized as a NOR logic gate and an INH logic gate.

Tandem Riboswitch Architectures Exhibit Complex Gene Control Functions

Riboswitches are structured RNAs typically located in the 5' untranslated regions of bacterial mRNAs that bind metabolites and control gene expression. Most riboswitches sense one metabolite and function as simple genetic switches. However, we found that the 5' region of the Bacillus clausii metE messenger RNA includes two riboswitches that respond to S-adenosylmethionine and coenzyme B12. This tandem arrangement yields a composite gene control system that functions as a two-input Boolean NOR logic gate. These findings and the discovery of additional tandem riboswitch architectures reveal how simple RNA elements can be assembled to make sophisticated genetic decisions without involving protein factors.

Not-So-Simple Switches

Riboswitches are structured RNAs that bind metabolites and, dependent on this binding, control gene expression. In most cases, the metabolite binding acts as a simple "on-off" switch. Now Sudarsan et al . report tandem riboswitch architectures that facilitate more sophisticated control. The 5′ untranslated region of Bacillus clausii metE RNA includes two riboswitches that respond independently to two different metabolites to function as a two-input Boolean NOR logic gate. N. Sudarsan, M. C. Hammond, K. F. Block, R. Welz, J. E. Barrick, A. Roth, R. R. Breaker, Tandem riboswitch architectures exhibit complex gene control functions. Science 314 , 300-304 (2006). [Abstract] [Full Text]

<inline-formula><math altimg="none" display="inline" overflow="scroll"><mrow><mn>40</mn><mspace width="0.3em" /><mi>Gbit</mi><mo>∕</mo><mi mathvariant="normal">s</mi></mrow></math></inline-formula> all-optical logic NOR gate based on a semiconductor optical amplifier and a filter

A novel all-optical logic NOR gate is presented that is composed of a semiconductor optical amplifier (SOA) and an optical bandpass filter. The NOR gate is successfully experimentally demonstrated at 40 Gbit/s. The experiment result shows good extinction ratio of larger than 12.0 dB with clear and open eye. The NOR gate has a simple configuration and allows photonic integration.

High speed logic gate using two-photon absorption in silicon waveguides

The switching speed of conventional silicon-based optical switching devices based on plasma dispersion effect is limited by the lifetime of free carriers which introduce either phase or absorption changes. Here we report an all-optical logic NOR gate which does not rely on free carriers but instead uses two-photon absorption. High speed operation was achieved using pump induced non-degenerate two-photon absorption inside the submicron size silicon wire waveguides. The device required low pulse energy (few pJ) for logic gate operation.

Ultrafast integrable and reconfigurable XNOR, AND, NOR, and NOT photonic logic gate

A novel, simple, compact, and integrable scheme of reconfigurable and ultrafast photonic logic gate is demonstrated, based on a single semiconductor optical amplifier (SOA) and able to process ultrafast signals. XNOR function has been optically implemented exploiting four-wave mixing and cross-gain modulation in an SOA. The same scheme can be easily reconfigured to obtain AND, NOR, and NOT logic gates. Performances in terms of bit error rate for 20-ps return-to-zero signals at 10 Gb/s show a power penalty limited to 0.5 dB for all logic gates but the AND, which experiences regeneration (-2-dB power penalty) due to nonlinear SOA noise compression.

40 Gbit/s all-optical logic NOR gate based on nonlinear polarisation rotation in SOA and blue-shifted sideband filtering

An all-optical logic NOR gate is presented by exploiting nonlinear polarisation rotation in a semiconductor optical amplifier (SOA) and blue-shifted sideband filtering. The NOR gate is experimentally demonstrated and simulated at 40 Gbit/s. Experimental results show high extinction ratio (ER) of about 12.2 dB with very clear and open eye. Simulation shows the scheme can provide excellent performance. The logic gate has a simple configuration and allows photonic integration.

Ultrafast all-optical NOR gate based on semiconductor optical amplifier and fiber delay interferometer

An ultrafast all-optical logic NOR gate based on a semiconductor optical amplifier (SOA) and a fiber delay interferometer (FDI) is presented. For high-speed input return-to-zero (RZ) signal, nonreturn-to-zero (NRZ) switching windows which satisfy Boolean NOR operation can be formed by properly choosing the delay time and the phase shift of FDI. 40Gb/s NOR operation has been demonstrated successfully with low control optical power. The factors that degrade the NOR operation have been discussed.

9-(Cycloheptatrienylidene)-fluorene Derivative: Remarkable Ratiometric pH Sensor and Computing Switch with NOR Logic Gate

2,7-Bis(4-dimethylaminophenyl)-9-(cycloheptatrienylidene)fluorene (1) was synthesized and characterized. 1 could be used as a fluorescent sensor either for pH or for pyridinium halide. Integrated with the ratiometric method and an NOR logic gate, a tunable two-input/multi-output system was presented on the basis of this single molecule. [structure: see text]

ZnO Nanorod Logic Circuits.

Logic devices, including OR, AND, NOT, and NOR gates, based on single-crystalline ZnO nanorods are demonstrated. In these devices, ZnO nanorods are employed as semiconducting channels. They control metal/oxide semiconductor junction characteristics, to yield either good ohmic or Schottky contacts, ensuring fabrication of high-performance Schottky diodes and metal-semiconductor field-effect transistors.

Theoretical analysis of all-optical spatial light modulation in organometallics based on triplet state absorption dynamics

We present a general theoretical analysis of all-optical spatial light modulation in organometallic compounds based on nonlinear excited-state absorption, considering the propagation effects of both read and write beams. A detailed analysis for Pt:ethynyl complex has been presented based on the rate equation approach and an analytical solution for the write beam transmission has been obtained. For typical values, the read beam at 633 nm is modulated by 97.9% with a write beam intensity of 100 kW/cm 2 at 355 nm. It is shown that the effect of write beam propagation in the medium is appreciable at low write beam intensities and the percentage modulation in Pt:ethynyl complex is larger than that in C 60 in toluene and ZnTPP. The characteristics have also been used to design all-optical NOT and the universal NOR and NAND logic gates.

A switchable macrocycle–clip complex that functions as a NOR logic gate

We have synthesized a new molecular switch-based on a macrocycle-clip complex-whose switching behavior not only can be controlled through the use of either K+-[2,2,2]cryptand or NH4+-Et3N systems but also provides color changes that are visible to the naked eye; consequently, this system operates as a two-input NOR functioning molecular logic gate.

Optoelectronic realisation of NOR logic gate using chaotic two-section lasers

Theoretical construction of the fundamental NOR gate using two-section laser diodes subject to optical injection is reported. Two self-pulsating laser diodes are commonly driven by a monochromatic light beam resulting in chaos and the logic gate is finally implemented by appropriately synchronising the two chaotic attractors.

Tunable all-optical NOR gate at 10 Gb/s based on SOA fiber ring laser

A novel scheme for a tunable all-optical logic NOR gate is presented that is based on a semiconductor fiber ring laser. In this new configuration a semiconductor optical amplifier is employed not only as the operational medium for cross-gain modulation effect to form a logic gate, but also as the active medium for a fiber ring laser that is designed to replace the continuous-wave light required in many other schemes. Alloptical logic NOR operation is successfully demonstrated experimentally by use of 10 Gb/s nonreturn-to-zero (NRZ) signals. An output extinction ratio higher than 10.3 dB can be obtained over the 40 nm tuning range except for a 4 nm gap around the input wavelength.

Photonic logic NOR gate based on two symmetric microring resonators

We demonstrate an all-optical NOR logic gate based on symmetric GaAs-AlGaAs microring resonators whose resonances are closely matched. Two input pump data streams are tuned close to one resonance of the symmetric microrings to switch a probe beam tuned to another resonance by two-photon absorption. The switching energy of the gate is 20 pJ/pulse, and the switching window is 40 ps, limited by the carrier lifetime. The use of two rings provides for better cascading in photonic logic circuits because of the higher number of available ports.

Pyrene-appended calix649crowned logic gates involving normal and reverse PET: NOR, XNOR and INHIBIT

As a novel sensing system, N-(1-pyrenylmethyl) amide-appended calix[4]crown-5 (2) and crown-6 (3) have been newly synthesized. Judging from the fluorescence changes upon the addition of cations, 3 having crown-6 ring showed the Pb2+ ion selectivity over other cations tested regarding fluorescence quenching. Upon the Pb2+ ion coordination to two amide oxygen atoms with aid of crown ring, a reverse-photo-induced electron transfer (PET) occurs in such a way that electrons transfer from the pyrene groups to the electron deficient amide oxygen atoms to give a quenched fluorescence. By the addition of either HClO4 or triethylamine in the solution of 3, the fluorescence intensity decreased because of the reverse-PET from pyrene groups to protonated amide oxygen atoms and because of normal PET from the nitrogen anion formed by triethylamine to pyrene groups, respectively. For 3, NOR logic gate in which the strong fluorescence signal appears at 395 nm (output: 1) is operated only when neither of triethylamine nor Pb(ClO4)2 (inputs A and B) is added (A=B: 0). XNOR gate is also operated only when both of two inputs are added (triethylamine and HClO4, A=B: 1) or when neither of two inputs is added (A=B: 0). Then, for 3, new INHIBIT gate system was also designed using such combinational inputs as HClO4, Pb(ClO4)2 and triethylamine.

Pyrene-appended calix[4]crowned logic gates involving normal and reverse PET: NOR, XNOR and INHIBIT

As a novel sensing system, N-(1-pyrenylmethyl) amide-appended calix[4]crown-5 ( 2 ) and crown-6 ( 3 ) have been newly synthesized. Judging from the fluorescence changes upon the addition of cations, 3 having crown-6 ring showed the Pb 2+ ion selectivity over other cations tested regarding fluorescence quenching. Upon the Pb 2+ ion coordination to two amide oxygen atoms with aid of crown ring, a reverse-photo-induced electron transfer (PET) occurs in such a way that electrons transfer from the pyrene groups to the electron deficient amide oxygen atoms to give a quenched fluorescence. By the addition of either HClO 4 or triethylamine in the solution of 3 , the fluorescence intensity decreased because of the reverse-PET from pyrene groups to protonated amide oxygen atoms and because of normal PET from the nitrogen anion formed by triethylamine to pyrene groups, respectively. For 3 , NOR logic gate in which the strong fluorescence signal appears at 395 nm (output: 1) is operated only when neither of triethylamine nor Pb(ClO 4) 2 (inputs A and B) is added (A=B: 0). XNOR gate is also operated only when both of two inputs are added (triethylamine and HClO 4, A=B: 1) or when neither of two inputs is added (A=B: 0). Then, for 3 , new INHIBIT gate system was also designed using such combinational inputs as HClO 4, Pb(ClO 4) 2 and triethylamine.

Digital logic gates using hot-phonon controlled superconducting nanotransistors

We describe the fabrication and digital switching operation of a NOR logic gate that uses a single, dual-input superconducting nanotransistor. The nanotransistor is a weak-link device that has integrated hot-phonon injectors to control its critical current. The fabrication process utilizes a self-aligned method, where the two heaters act as a mask for reactive ion etching to define the device pattern. This device is much simpler to fabricate than previously reported superconducting transistors and the principle of operation makes it possible to use a single nanotransistor, with multiple input heaters, as a NOR logic gate, allowing lower power consumption and improved levels of integration.

All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers

The authors present a novel all-optical logic NOR gate using two-cascaded semiconductor optical. amplifiers (SOAs) in a counterpropagating feedback configuration. This configuration accentuates the gain nonlinearity due to the mutual gain modulation of the two SOAs. The all-optical NOR gate feasibility has been demonstrated delivering an extinction ratio higher than 12 dB over a wide range of wavelength.