All-silicon integrated optical modulator

The authors describe the operating principle, design, and performance of an all-silicon light modulator at 1.3 μm wavelength. The modulator is based on the plasma effect in silicon and the mode selectivity of single-mode optical fibers, resulting in low polarization dependence and the capability of handling high light intensities. Standard silicon IC technology is used in the fabrication process and the modulator has a vertical structure that takes up a small surface area (the active area matches the single-mode fiber core of 9 μm diameter), simplifying integration with other circuitry on the same chip. The modulator can be directly coupled to a single-mode optical fiber, without using lenses or other bulk optical components. Typical performance of the fabricated modulators is 6 dB insertion loss, 24% modulation depth, and 60 MHz bandwidth with a current drive of 22 mA rms     

Fiber-optic magnetic-force phase modulator

A fiber-optic magnetic-force phase modulator using an aluminium-jacketed current-carrying fiber coil placed in a uniform external magnetic field is presented. The modulator has a center frequency of 30 kHz with a modulation efficiency of 2.4 rad/mA and a Q of 4.6. A theoretical model is developed for the modulator, and its predictions are compared with experimental results. An accurate and simple method of characterizing the phase modulator response is described     

Microbial uptake of cadmium and its effects on the biochemical oxygen demand at various temperatures

Uptake of cadmium by microbes at different temperatures has been studied at pH 7. Glycine was used as a source of carbon for microorganisms in the BOD bottle at 20, 30, 40 and 50°C with varying concentrations of cadmium: control 0.0437, 0.437, 0.875 and 1.31 mg 1⁻¹ in each set. The influence of temperatures on the toxic effects of cadmium has been studied with respect to rate constant (k) and ultimate biochemical oxygen demand which were calculated from BOD data using Thomas Graphical method. Consumed cadmium mg 1⁻¹ was determined after eight days and it varied from 14.04 to 32.40% at four temperatures. Highest consumption of Cd was noted in the set at 30 and 40°C and lowest at 50°C.     

Resource Management in UAV Enabled MEC Networks

Mobile edge cloud networks can be used to offload computationally intensive tasks from Internet of Things (IoT) devices to nearby mobile edge servers, thereby lowering energy consumption and response time for ground mobile users or IoT devices. Integration of Unmanned Aerial Vehicles (UAVs) and the mobile edge computing (MEC) server will significantly benefit small, battery-powered, and energy-constrained devices in 5G and future wireless networks. We address the problem of maximising computation efficiency in U-MEC networks by optimising the user association and offloading indicator (OI), the computational capacity (CC), the power consumption, the time duration, and the optimal location planning simultaneously. It is possible to assign some heavy tasks to the UAV for faster processing and small ones to the mobile users (MUs) locally. This paper utilizes the k-means clustering algorithm, the interior point method, and the conjugate gradient method to iteratively solve the non-convex multi-objective resource allocation problem. According to simulation results, both local and offloading schemes give optimal solution.     

Photoresponse properties of BaSi2 epitaxial films grown on the tunnel junction for high-efficiency thin-film solar cells

We have successfully grown 360-nm-thick undoped n-BaSi₂ epitaxial layers on the n⁺-BaSi₂/p⁺-Si(111) tunnel junction, by molecular beam epitaxy. The external quantum efficiency reached approximately 17.8% at 500 nm under a reverse bias voltage of 4 V at room temperature, the highest value ever reported for semiconducting silicides. The quantum efficiency was compared to 240-nm-thick undoped n-BaSi₂ epitaxial layers on a p-Si(111) substrate.     

Phyto‐fabrication,purification, characterisation,optimisation, and biological competence of nano‐silver

Published studies indicate that virtually any kind of botanical material can be exploited to make biocompatible, safe, and cost‐effective silver nanoparticles. This hypothesis is supported by the fact that plants possess active bio‐ingredients that function as powerful reducing and coating agents for Ag+. In this respect, a phytomediation method provides favourable monodisperse, crystalline, and spherical particles that can be easily purified by ultra‐centrifugation. However, the characteristics of the particles depend on the reaction conditions. Optimal reaction conditions observed in different experiments were 70–95 °C and pH 5.5–8.0. Green silver nanoparticles (AgNPs) have remarkable physical, chemical, optical, and biological properties. Research findings revealed the versatility of silver particles, ranging from exploitation in topical antimicrobial ointments to in vivo prosthetic/organ implants. Advances in research on biogenic silver nanoparticles have led to the development of sophisticated optical and electronic materials with improved efficiency in a compact configuration. So far, eco‐toxicity of these nanoparticles is a big challenge, and no reliable method to improve the toxicity has been reported. Therefore, there is a need for reliable models to evaluate the effect of these nanoparticles on living organisms.     

Density-Controlled Metal Nanocluster with Modulated Surface for pH-Universal and Robust Water Splitting

Reducing the particle sizes of transition metals (TMs) and avoiding their aggregation are crucial for increasing the TMs atom utilization and enhancing their industrial potential. However, it is still challenging to achieve uniform distributed and density-controlled TMs nanoclusters (NCs) under high temperatures due to the strong interatomic metallic bonds and high surface energy of NCs. Herein, a series of TMs NCs with controllable density and nitrogen-modulated surface are prepared with the assistance of a selected covalent organic polymer (COP), which can provide continuous anchoring sites and size-limited skeletons. The prepared Ir NCs show superior hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities than commercial Pt/C and Ir/C in both acid and alkaline media. In particular, the as-prepared Ir NCs exhibit remarkable full water splitting performance, reaching a current density of 10 mA cm⁻² at ultralow overpotentials of 1.42 and 1.43 V in alkaline and acidic electrolyte, respectively. The excellent electrocatalytic activities are attributed to the increased surface atom utilization and the improved intrinsic activity of Ir NCs. More importantly, the Ir NCs catalyst shows superior long-term stability due to the strong interaction between Ir NCs and the N-doped carbon layer.