Narrow Results

Recent progress in the domain of time and frequency standards has required some important improvements of existing time transfer links. Several time transfer by laser link (T2L2) projects have been carried out since 1972 with numerous scientific or technological objectives. There are two projects currently under exploitation: T2L2 and Lunar Reconnaissance Orbiter (LRO). The former is a dedicated two-way time transfer experiment embedded on the satellite Jason-2 allowing for the synchronization of remote clocks with an uncertainty of 100 ps and the latter is a one-way link devoted for ranging a spacecraft orbiting around the Moon. There is also the Laser Time Transfer (LTT) project, exploited until 2012 and designed in the frame of the Chinese navigation constellation. In the context of future space missions for fundamental physics, solar system science or navigation, laser links are of prime importance and many missions based on that technology have been proposed for these purposes.

Current model for circadian rhythms is wrong both theoretically and practically. A new model, called yin yang model, is proposed to explain the mechanism of circadian rhythms. The yin yang model separate circadian activities in a circadian system into yin (night activities) and yang (day activities) and a circadian clock into a day clock and a night clock. The day clock is the product of night activities, but it promotes day activities; the night clock is the product of day activities, but it promotes night activities. The clock maintains redox or energy homeostasis of the internal environment and allows temporal separations between biological processes with opposite impacts on the internal environment of a circadian system.

Fractal geometry can adequately represent many complex and irregular objects in nature. The fractal dimension is typically computed by the box-counting procedure. Here I compute the box-counting and the Kaplan-Yorke dimensions of the 14-dimensional models of the Drosophila circadian clock. Clockwork Orange (CWO) is transcriptional repressor of direct target genes that appears to play a key role in controlling the dynamics of the clock. The findings identify these models as strange attractors and highlight the complexity of the time-keeping actions of CWO in light-day cycles. These fractals are high-dimensional counterexamples of the Kaplan-Yorke conjecture that uses the spectrum of the Lyapunov exponents.

A new transistor-less field-coupled nanocomputing (FCN) method for ultra-scale “nanochip” integration is called quantum-dot cellular automata (QCA). Electrostatic repulsion between electrons and the electron tunneling process in quantum dots is employed in QCA to depict digital circuitry. QCA technology is able to achieve higher clock speed, lower occupied chip area, and more energy efficiency than traditional complementary metal-oxide semiconductor (CMOS) technology. Irreversible majority gates are commonly utilized as the main building blocks in the development of QCA circuits. In order to create highly energy-efficient QCA circuits, some research has recently presented digital image processing design strategies that use majority gates as the primary building block. Image processing, which encompasses picture analysis, enhancement, and correction, is used to extract information from images and improve their quality. Among the primary methods for processing images are picture enhancement, restoration, compression, object recognition, and machine vision applications. However, morphological procedures such as dilation and erosion constitute the fundamental component of image processing and are widely applied in practical applications. In this study, QCA-optimized nanostructures are presented for applications in mathematical morphology, serving as erosion and dilation operators. The completed circuit comprises 33 cells and exhibits a temporal delay of approximately 0.75 during each clock cycle. A comparison with the best equivalent nano-architecture demonstrates a significant improvement in cell performance, scalability, and latency.

For the first time to our knowledge, we experimentally demonstrate a clock signal transmission using a counter-propagating Raman pump as a transmitter and concurrently utilize the same pump to amplify a data signal. A 1548nm vertical cavity surface emitting laser (VCSEL) was modulated with a pseudorandom bit sequence (2${}^7-1$) and coupled into an optical fiber. A 1448nm Raman pump in the backward scheme was also modulated with a 10kHz clock and used to boost the VCSEL data signal so as to improve the reach of the transmission. Clock distribution in a telescope network such as the Square Kilometre Array (SKA) is essential for the proper operation of the digitizers as well as dish synchronization. In the SKA phase 1, long transmissions involving baselines extending up to 100km may need amplification. We propose the use of counter-Raman configuration to amplify the signal carrying received astronomical data while transmitting a clock to the receptors. This is a cost-effective bi-directional transmission suited for telescope network applications.

Recent progress in the domain of time and frequency standards has required some important improvements of existing time transfer links. Several time transfer by laser link (T2L2) projects have been carried out since 1972 with numerous scientific or technological objectives. There are two projects currently under exploitation: T2L2 and Lunar Reconnaissance Orbiter (LRO). The former is a dedicated two-way time transfer experiment embedded on the satellite Jason-2 allowing for the synchronization of remote clocks with an uncertainty of 100 ps and the latter is a one-way link devoted for ranging a spacecraft orbiting around the Moon. There is also the Laser Time Transfer (LTT) project, exploited until 2012 and designed in the frame of the Chinese navigation constellation. In the context of future space missions for fundamental physics, solar system science or navigation, laser links are of prime importance and many missions based on that technology have been proposed for these purposes.