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We characterize the instability of an rf clock signal caused by free-space transmission of a frequency comb (FC) under typical laboratory conditions. The phase-noise spectra show the involvement of multiple random processes. For a 10 m transmission, the rms timing jitter integrated over 1-10(5) Hz is 95 fs, and the root Allan variance over 1 s is 4x10(-13). The measured Allan variance has a tau(-1) behavior and an excellent agreement with the phase noise measurement. These results indicate the feasibility of FC-based free-space rf clock distribution over short distances.

The foundation of any smart city requires an innovative and robust communication infrastructure. Many research communities envision free-space optical communication (FSO) as a promising backbone technology for the services and applications provided by such cities. However, the channel through which the FSO signal travels is the atmosphere. Therefore, the FSO performance is limited by the local weather conditions. The variation in meteorological variables leads to variations of the refractive index along the transmission path. These index inhomogeneities (i.e., atmospheric turbulence) can significantly degrade the performance of FSO systems. Thus, a practical implementation of the FSO link must carefully consider the atmospheric turbulence effect. This paper aims to investigate the feasibility of FSO communication for NEOM, a promising smart city in Saudi Arabia. We study the effect of weather conditions on FSO links using the micrometeorology model, taking into account actual weather data. The FSO performance in winter and summer was compared in terms of the bit error rate, signal-to-noise ratio (SNR), link availability, and transmission distance. The study shows that the atmospheric turbulence strength is moderate and strong in winter and summer, respectively. The temperature has the biggest impact on the FSO system when compared to the other meteorological elements included in this study. Furthermore, at transmission distances less than 300 m, atmospheric turbulence does not significantly affect the FSO for the operating wavelength of 1550 nm. Furthermore, it has been shown that at transmission distances greater than 300 m, the SNR in summer is more than 18% higher than in winter. The findings of this research enable understanding of the effect of turbulence caused by NEOM weather on the FSO link, thus assisting engineers in establishing a reliable FSO backbone link by adjusting the relevant parameters.

No abstract

Escherichia coli is an important pollution indicator and is the most important foodborne pathogens of public health concern. The chicken meat is one of the most important sources of good quality protein, and it is also susceptible to microbial contamination and often implicated in foodborne disease. In such context, the detection of E. coli K12 in frozen chicken meat was investigated by electrochemical impedance spectroscopy and surface plasmon resonance imaging techniques. The anti‐E. coli antibody was first immobilized onto gold surface by physisorption technique. The electrical and optical properties of the immobilized anti‐E. coli K12 antibody were studied. The binding of the E. coli K12 bacteria with the anti‐E. coli antibody layer was measured with a detection limit of 103 cfu/ml. This detection limit is better than those obtained with the enzyme‐linked immunosorbent assay (ELISA) technique. Moreover, the developed biosensor was used for E. coli K12 detection in inoculated frozen chicken meat. Practical applications Escherichia coli is an important pollution indicator and is the most important foodborne pathogens of public health concern. The present study deals with the development of bacteria biosensors based on electrochemical impedance spectroscopy and surface plasmon resonance imaging techniques for E. coli K12 detection in inoculated frozen chicken meat. A detection limit of 103 cfu/ml was obtained with the developed biosensors that was better than those obtained with classical methods such as ELISA (enzyme‐linked immunosorbent assay). This research work opens tremendous potential applications for the detection of pathogens in food at the early stage particularly with the development of miniaturized multiarrays platform based on impedance spectroscopy.