EDFA Gain-Flattening Using Side-Polished Fiber Half-Coupler With an Overlay Waveguide

We report fabrication and modeling of a fiber half-coupler based gain-flattening device for EDFA. Using such a device, flattening of the ASE spectrum of an EDFA is also demonstrated.     

Giant Phononic Anisotropy and Unusual Anharmonicity of Phosphorene: Interlayer Coupling and Strain Engineering

Phosphorene, an emerging elemental 2D direct band gap semiconductor with fascinating structural and electronic properties distinctively different from other 2D materials such as graphene and MoS₂, is promising for novel nanoelectronic and optoelectronic applications. Phonons, as one of the most important collective excitations, are at the heart of the device performance, as their interactions with electrons and photons govern the carrier mobility and light‐emitting efficiency of the material. Here, through a detailed first‐principles study, it is demonstrated that monolayer phosphorene exhibits a giant phononic anisotropy, and remarkably, this anisotropy is squarely opposite to its electronic counterpart and can be tuned effectively by strain engineering. By sampling the whole Brillouin zone for the monolayer phosphorene, several “hidden” directions are found, along which small‐momentum phonons are “frozen” with strain and possess the smallest degree of anharmonicity. Unexpectedly, these “hidden” directions are intrinsically different from the usually‐studied armchair and zigzag directions. Light is also shed on the anisotropy of interlayer coupling of few‐layer phosphorene by examining the rigid‐layer vibrations. These highly anisotropic and strain‐tunable characteristics of phosphorene offer new possibilities for its applications in thermal management, thermoelectronics, nanoelectronics, and phononics.     

Design,synthesis, evaluation,and molecular dynamic simulation of triclosan mimic diphenyl ether derivatives as antitubercular and antibacterial agents

In the present work, we have explored triclosan mimic diphenyl ether derivatives as inhibitors of Mycobacterium tuberculosis enoyl acyl carrier protein reductase (InhA) using a structure-based drug design approach. The virtual library of diphenyl ethers was designed and compounds with acceptable absorption, distribution, metabolism, excretion, and toxicity properties were docked. The compounds with higher dock score (5a-g) than triclosan were synthesized, characterized, and evaluated for in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv. Among the synthesized compounds, compounds 5f and 5c appeared to be the most promising with minimum inhibitory concentration of 18 μM and 36 μM respectively. The molecular dynamics simulation study of the most active compound 5f and triclosan was performed, which correlates with its activity in comparison with triclosan. All the compounds were further evaluated for cytotoxicity studies against Vero, and HepG2 were found to be safe. Furthermore, compound 5f was evaluated for in vitro cytotoxicity against mouse macrophage cell lines (RAW 264.7), and the study indicated its safety in eukaryotes at 50-μM concentration. In addition, compounds 5a-g were also screened for their in vitro antibacterial activity against two gram-positive and two gram-negative bacteria by resazurin-based microtiter dilution assay method. Among the synthesized compounds, 5f and 5b appeared to be promising, against various gram-positive and gram-negative microorganisms, indicating its broad-spectrum potential.

     

In-line phase separator for microfluidic solvent extraction of uranium

Experiments are carried out to study the separation of liquid-liquid dispersion generated at a microfluidic junction by using an in-line phase separator. The phase separator comprises a metallic mesh sandwiched between two flow channels. Dispersion generated at the microfluidic junction is fed to the upper flow channel of the in-line phase separator. Continuous phase permeates through the metallic mesh into the lower flow channel and gets separated from the dispersed phase. The effects of operating parameters (flow rates of the aqueous and organic phases), flow channel geometry and mesh properties (pore size and thickness) on phase separation are studied. After identification of operating window in which complete phase separation is achieved, mass transfer experiments are performed to demonstrate intensified uranium extraction using a micromixer and in-line phase separator.

     

Standardisation of radioimmunoassay for human insulin employing magnetizable cellulose particles

We describe a convenient and flexible solid phase radioimmunoassay for human insulin employing magnetizable cellulose particles. Anti-porcine insulin antibody was covalently linked to magnetizable cellulose particles to form a stable and economical solid phase immunosorbent system. The tracer was prepared by radioiodinating insulin with ¹²⁵I using Chloramine-T oxidation method. The analytical sensitivity of assay observed was 5.5 μIU/mL. Intra-assay and inter-assay variations were found to be <12 % along with analytical recovery of 93–109 %. The developed assay can be used for the routine analysis of clinical samples. In addition, concentration of the solid phase magnetizable immunosorbent can be easily varied as per the specific requirement for research purposes.     

Optimized rule-based delay proportion adjustment for proportional differentiated services

We present a novel method to adjust output queue delay proportion fairly among traffic classes of different priorities in relative differentiated services. The delay proportion adjustment is based on acceleration of incoming traffic in each class. It aims to reduce the undesirable effects of queue-delay propagation toward higher priority classes, caused by the introduction of bursty data into lower priority classes. We use a fuzzy controller to make the decision regarding the amount of proportion adjustment, as it is very flexible and adjustable. We suggest an efficient extension to the particle swarm optimization algorithm for the purpose of optimizing the fuzzy system. The simulation shows that the dependency of high-priority-class delay, which is a value that indicates quality-of-service of the traffic, on lower priority classes is significantly reduced by the proposed delay proportion adjustment.     

Rotational viscosity and molecular structure of nematic liquid crystals

An electro-optical technique was used to measure the rotational viscosity of nematic liquid crystals, whose structures were chosen to investigate the effects of linking groups and lateral groups on rotational viscosity. These results are compared with the theory developed by Osipov and Terentjev. It is shown that the theory is useful in predicting rotational viscosity for specific molecular structures. The agreement between theory and experiment is found to be good for all the liquid crystals studied.     

Finding the reconstructions of semiconductor surfaces via a genetic algorithm

In this article we show that the reconstructions of semiconductor surfaces can be determined using a genetic procedure. Coupled with highly optimized interatomic potentials, the present approach represents an efficient tool for finding and sorting good structural candidates for further electronic structure calculations and comparison with scanning tunneling microscope (STM) images. We illustrate the method for the case of Si(1 0 5), and build a database of structures that includes the previously found low-energy models, as well as a number of novel configurations.     

Elevated temperature stability of GaAs digital integrated circuits

The elevated temperature stability of a commercial GaAs enhancement-depletion-mode MESFET process has been characterized; the observations made are relevant to device operation at elevated temperatures, with implications for optoelectronic integration on GaAs integrated circuits by selective-area epitaxial growth, and to long term circuit and device reliability. Although the transistor electrical characteristics are stable for up to five hours at 500°C, a metallurgical reaction between the interconnect metal AlCu_x core and WN_x claddings has been identified which limits circuits to five hour operation at 470°C. This later reaction proceeds with an activation energy of 3.5 eV and results in a 15-fold increase in interconnect metal sheet resistance. A geometry-dependent increase in ohmic contact resistance is seen at somewhat higher temperature which is ascribed to the penetration of aluminum-containing compounds to the ohmic contact edge     

Signal modeling and detection using cone classes

A new signal model-the cone classes-is presented. These models include classical models such as subspaces but are more general and potentially more useful than some existing signal models. Examples of cone classes include time-frequency concentrated classes and subspaces with bounded mismatch. The maximum likelihood detector for a cone class of signals in the presence of Gaussian noise is derived, and a simple algorithm is suggested as a possible detector implementation. The detector is examined in the specific case of subspaces with bounded mismatch. It is shown that there are conditions under which this detector has a higher detection probability for fixed false alarm than that of a comparable subspace detector and energy detector