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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.

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In this work, solid flexible polymer blend electrolytes (PBE) composed of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) with different amounts of sodium thiocyanate (NaSCN) salt mixed in double-distilled water (solvent) are prepared via solution casting method. The obtained films are characterized using several techniques. The study of the surface morphology of the polymer blend salt complex films via the POM technique reveals the presence of amorphous regions due to the NaSCN effect. FTIR spectra studies confirm the complex formation between PVA, PVP, and NaSCN. The addition of 20 wt% NaSCN salt in the composition PVA: PVP (50:50 wt%) polymer blend matrix leads to an increase in the number of charge carriers and thus improves the ionic conductivity. The ionic conductivity of each polymer blend electrolyte was studied using the electrochemical impedance spectroscopy (EIS) method. The highest room temperature ionic conductivity of 8.1 × 10−5 S/cm S cm−1 is obtained for the composition of PVA: PVP (50:50 wt%) with 20 wt% NaSCN. LSV test shows the optimized ion-conducting polymer blend electrolyte is electrochemically stable up to 1.5 V. TNM analysis reveals that 99% of ions contribute for the conductivity against 1% of electrons only in the highly conductive polymer electrolyte PVA: PVP (50:50 wt%) + 20 wt% NaSCN. A supercapacitor device was fabricated using the optimized ion-conducting polymer blend film and graphene oxide (GO) coated electrodes. The GCD curve clearly reveals the behavior of an ideal capacitor with less Faradic process and low ESR value. The columbic efficiency of the GO-based system is found to be 100%, the GO-based electrode exhibits a specific capacitance of 12.15 F/g and the system delivers the charge for a long duration. The specific capacitance of the solid-state supercapacitor cell was found to be 13.28 F/g via the CV approach close to 14.25 F/g obtained with EIS data at low frequency.

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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.

We report on a facile strategy towards fabrication and testing of tungsten oxide and gold nanoparticles decorated PEDOT-PSS ternary nanocomposite (PEDOT: PSS-WO2-Au) as a flexible electrode material for supercapacitor applications. The morphological and structural features of the bare PEDOT-PSS and PEDOT: PSS-WO2-Au ternary nanocomposites were analyzed through scanning electron microscopy and Fourier transforms infra-red spectroscopy, whereas the thermal stability of the samples was studied through theromogravimetric analysis. The presence of Au nanoparticles significantly enhances the room temperature conductivity from 3 S cm−1 for bare PEDOT-PSS to 1552 S cm−1 for the ternary composite. This ternary composite electrode displays superior electrochemical performance with a specific capacitance of 462 Fg−1 in comparison to 112 Fg−1 for bare PEDOT-PSS and 359.25 Fg−1 for PEDOT-PSS: WO2 composite. The nanocomposite electrode displays capacitance retention of ∼92% after 5000 cycles of operation. The investigated ternary electrode shows excellent flexibility without capacitance fading under bending and rolling conditions.

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.