Efficient procedures for the optimization of defects in photonic crystal structures

Seven different stochastic binary optimizers--based on the concepts of genetic algorithms and evolutionary strategies--are developed, applied to determine defect locations in several photonic crystal structures that serve as test cases, and compared by extensive statistical analysis. In addition to the stochastic optimizers, a quasi-deterministic optimizer based on an algorithm inspired by hill-climbing algorithms was implemented. The test cases include the prominent 90 degrees photonic crystal waveguide bend and a photonic crystal power divider. The analysis of the results shows that many different photonic crystal structures with high transmission may be found for any operating frequency. All of the eight optimizers outperform standard codes-because they maintain an incomplete fitness table-and find the global optima with a high probability even when the number of fitness evaluations is much smaller than the number of potential solutions contained in the discrete search space. Based on the incomplete fitness table, an algorithm to estimate bit-fitness values is presented. The bit-fitness values are then used to improve the performance of some algorithms. The four best algorithms-an extended microgenetic algorithm, two mutation-based algorithms, and the quasi-deterministic algorithm inspired by hill-climbing algorithms-are considered to be of high value for the optimization of defects in photonic crystals and for similar binary optimization problems.     

Development of a Metabolically Stable Neurotensin Receptor 2 (NTS2) Ligand

Subtype‐selective neurotensin receptor 2 (NTS2) ligands can be used as molecular probes to investigate the physiological role of neurotensinergic systems and serve as lead compounds to initiate the development of drugs for the treatment of tonic pain. Starting from our recently described NTS2 ligand 1 , structural variants of type 2 were synthesized to further improve binding affinity and selectivity to gain metabolic stability. The peptide–peptoid hybrid 2 b showed excellent NTS2 binding affinity (K_i=2.8 nM ) and 22 000‐fold selectivity over NTS1, as well as metabolic stability over 32 h in a serum degradation assay. Employing a MAPK‐driven luciferase reporter gene assay and an IP accumulation assay, the neurotensin mimetic 2 b displayed respective inhibitions of constitutive activity exceeding 4.3‐ and 3.9‐fold that of the inverse agonist activity of the endogenous ligand neurotensin.     

Development of lightweight high‐performance polymeric composites with functionalized nanotubes

In this article, we highlight the various properties of an ultralightweight poly(ether ketone) (PEK) composite. In this study, special emphases were laid on the preparation of low‐density, high‐performance polymeric foams with foaming agents and activators. PEK, foamed PEK, and carbon nanotube (CNT)–reinforced foamed PEK composites were considered for this study. The density of the polymer decreased with the reinforcement of the foaming agent. We also noted that with the reinforcement of the modified CNT in the foamed PEK, there were marginal increases in the density and hardness of the composites. We also noted that the mechanical properties of the CNT‐reinforced foamed PEK was on par with those of basic PEK. Thermogravimetric analysis gave us a clear indication that the thermal stability of the composites was not affected by the reinforcing foaming agent and nanoparticles. Scanning electron microscopy and transmission electron microscopy clearly indicated the formation of foams and also the dispersion of nanoparticles in the composite structure. We also observed that because of the reinforcement of multiwalled CNTs in the composite, there was an improvement in the hardness of the composite. An increase in the specific strength was observed in the foamed PEK composites. The CNT‐reinforced foamed PEK showed a marginal decrease in the specific strength without a compromise in the impact strength. The impact strength of the CNT‐reinforced foamed PEK composite was found to be similar to that of the basic PEK. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43471.     

Novel polyurethane dispersions based on renewable raw materials—Stability studies by variations of DMPA content and degree of neutralisation

Renewable resources, especially natural oils, have received increasing attention as raw materials for polymers. The synthesis and characterisation of novel aqueous polyurethane dispersions derived from rapeseed oil are investigated. The applied renewable polyol is high-hydrophobic due to the triglyceride backbone. Dimethylolpropionic acid (DMPA) as internal emulsifier was used to incorporate hydrophilic groups into the polymer chain to achieve stable self-emulsifying dispersions. By neutralisation of the carboxyl groups with triethylamine a predominately electrostatic stabilisation was generated. A weak steric stabilisation by pending chain ends exists beside the predominant electrostatic stabilisation. Outgoing from a DMPA content of 5.6 wt% related to the polymer, the content was decreased successively with the objective being to analyse the influence of ionic concentration and stability. Furthermore, the influence of the degree of neutralisation with respect to the stabilisation of these novel dispersions was investigated.     

Chemical Validation of DegS As a Target for the Development of Antibiotics with a Novel Mode of Action

Despite the availability of hundreds of antibiotic drugs, infectious diseases continue to remain one of the most notorious health issues. In addition, the disparity between the spread of multidrug-resistant pathogens and the development of novel classes of antibiotics exemplify an important unmet medical need that can only be addressed by identifying novel targets. Herein we demonstrate, by the development of the first in vivo active DegS inhibitors based on a pyrazolo[1,5-a]-1,3,5-triazine scaffold, that the serine protease DegS and the cell envelope stress-response pathway σE represent a target for generating antibiotics with a novel mode of action. Moreover, DegS inhibition is synergistic with well-established membrane-perturbing antibiotics, thereby opening promising avenues for rational antibiotic drug design.     

Pilot study of intrauterine exposure to methylmercury in Eastern Aegean islands, Greece

A group of islands with a total population of about 200,000 was identified in the Eastern Aegean, where there was evidence to suggest possible increased exposure to methylmercury (MeHg) through consumption of fresh local fish and other seafood from seas bordered by mercury-bearing rock. A feasibility study was conducted to explore the possibility of defining a local population of mother-child pairs in whom to investigate the intrauterine exposure effect. Analysis of 246 hair samples collected from pregnant women and mothers of newborn babies and children under 5 years showed levels of total Hg from 0.046 microg/g to 17.5 microg/g, geometric mean 1.36 microg/g, and of MeHg from 0.031 microg/g to 16.2 microg/g, geometric mean 1.07 microg/g. About 5% of the mothers had hair total Hg levels in excess of 6.00 microg/g. Investigation of dietary habits showed that one-third of the mothers eat fresh local fish at least 3 times weekly, one-third once a week and 10% rarely or never. There was a close association between weekly rates of local fish consumption and hair levels of both total Hg and MeHg. A power calculation determined that a cohort of 3000 mother-child pairs would enable comparison of a high-exposure group (those with the upper 5% of hair MeHg) with a low exposure group (5%, selected from those with the lower 30% of hair MeHg, matched for confounding factors), in order to detect an effect size of 0.35 to 0.45 at a power of 85-95%. It is concluded that the mothers and children in the Eastern Aegean islands studied comprise a population suitable for an epidemiological study of the effects of intrauterine exposure to MeHg via maternal fresh local fish consumption.     

Observer-based control for high order delayed systems with an unstable pole and a pole at the origin

Time delays in dynamical systems are challenging when trying to control them. One of the most common techniques consists in estimating one or more signals of interest before they are delayed, in order to use them in the control stage. In this work, an observer-based control strategy for unstable linear systems with a pole at the origin and delay is suggested. Also, the proposed observer is extended to be used in the case of a high order unstable delayed system. Likewise, the conditions to ensure the existence of the proposed observer-predictor are presented. A methodology is introduced to obtain the observer parameters. The proposed observer scheme makes use of a Proportional-Integral-Derivative control that makes it possible to ensure the tracking of step-type references and the rejection of disturbances of the same type in the closed-loop system.     

Evolutionary Design of Fuzzy Logic Based Position Controller for Mobile Robot

This paper develops a fuzzy logic based position controller whose membership functions are tuned by genetic algorithm. The main goal is to ensure successful velocity and position trajectories tracking between the mobile robot and the virtual reference cart. The proposed fuzzy controller has two inputs and two outputs. The first input represents the distance between the mobile robot and the reference cart. The second input is the angle formed by the straight line defined with the orientation of the robot, and the straight line that connects the robot with the reference cart. The outputs represent linear and angular velocity commands, respectively. The performance of the fuzzy controller is validated through comparison with previously developed mobile robot position controller based on control Lyapunov functions (CLF). Simulation results indicate good performance of position tracking while at the same time a substantial reduction of the control torques is achieved.