Design and performance analysis of a nanogyroscope based on electrostatic actuation and capacitive sensing

In this paper, a vibrating beam gyroscope with high operational frequencies at mode-matched condition is proposed. The model comprises a micro-cantilever with attached tip mass operating in the flextural–flextural mode. The drive mode is actuated via the electrostatic force, and due to the angular rotation of the base about the longitudinal axis. The secondary sub-nanometric vibration is induced in the sense direction which causes a capacitive change in the sense electrodes. The coupled electro-mechanical equation of motion is derived using the extended Hamilton's principle, and it is solved by direct numerical integration method. The gyroscope performance is investigated through the simulation results, where the device dynamic response, rate sensitivity, resolution, bandwidth, dynamic range, g$g$ sensitivity and shock resistance are studied. The obtained results show that the proposed device may have better performance compared to commercial micro electromechanical gyroscope characteristics.     

Nonlinear analysis of thermoelastic damping in axisymmetric vibration of micro circular thin-plate resonators

Thermoelastic damping is a source of dissipation in micro scale circular plate resonators. In contrast to previous researches, in this study thermoelastic damping is derived considering nonlinear effects. The microplate is assumed as a clamped circular plate. The microplate is modeled using the von Karman hypothesis along with Hamilton principle. Finally for harmonic vibrations, by using Kantorovich time averaging technique and perturbation techniques, thermoelastic damping is derived. The behavior of thermoelastic damping versus material properties, environmental temperature, plate radius and plate thickness are plotted. In this study the difference between linear and nonlinear analysis is shown for calculation of thermoelastic damping. The results show that the nonlinear analysis has a significant influence on thermoelastic damping coefficient.     

Prediction of different antibacterial activity in a new set of formyl hydroxyamino derivatives with potent action on peptide deformylase using structural information

Due to the essential role of peptide deformylase (PDF) at the bacterial growth cycle, it is a noteworthy target for developing a novel antibacterial agent. In the current study, the antibacterial activities of a set of 44 new structures of formyl hydroxyamino derivatives as PDF inhibitors were quantified using quantitative structure–activity relationship (QSAR). Artificial neural networks (ANN) were used as a chemometrics tool for QSAR modeling. Three quantitative models were suggested to relate the chemical structural features of the formyl hydroxyamino derivatives to their antibacterial activities (pIC₅₀) against Staphylococcus aureus, methicillin-susceptible S. aureus (MSSA), and methicillin-resistant S. aureus (MRSA) peptide deformylase. The sufficiency of the model for prediction of the antibacterial activities of the desired PDF inhibitor compounds against S. aureus, MSSA, and MRSA was statistically demonstrated according to the validation parameters such as coefficient of determination (R²), mean square error (MSE) in training, validation, and prediction sets, and also using applicability domain (AD) and randomization test.

     

Preparation and characterization of polyimides containing triaryl imidazole side groups

A novel triaryl imidazole‐containing diamine, 3,5‐diamino‐N‐(4‐(4,5‐diphenyl‐1H‐imidazol)phenyl)benzamide, was successfully synthesized via the condensation of 4‐(4,5‐diphenyl‐1H‐imidazol)benzenamine and 3,5‐dinitrobenzoyl chloride, followed by reduction of the dinitro compound. A series of new aromatic polyimides with pendent triaryl imidazole moieties were prepared from the reaction of this diamine with various tetracarboxylic dianhydrides by a conventional two‐step polymerization process via thermal and chemical imidizations. The polyimides were obtained in quantitative yields with inherent viscosities of 0.21–0.44 dL/g. All the polymers are readily soluble in polar organic solvents. Flexible and strong films of polyimides were obtained by solution casting. The glass transition temperature of these polymers was in the range of 261–264°C. They were fairly stable up to a temperature around 300°C and lost 10% weight at 408°C under nitrogen. The ultraviolet–visible absorption spectra showed that all of the polymers had absorption maxima around 320 nm with a fluorescence emission maxima around 388–407 nm in N‐methyl‐2‐pyrrolidinone solution. Cyclic voltammograms of the polyimides revealed an oxidation wave with a peak around 1.7 V. Copyright © 2016 John Wiley & Sons, Ltd.     

Application of MOS Gas Sensors Coupled with Chemometrics Methods to Predict the Amount of Sugar and Carbohydrates in Potatoes

Five potato varieties were studied using an electronic nose with nine MOS sensors. Parameters measured included carbohydrate content, sugar level, and the toughness of the potatoes. Routine tests were carried out while the signals for each potato were measured, simultaneously, using an electronic nose. The signals obtained indicated the concentration of various chemical components. In addition to support vector machines (SVMs that were used for the classification of the samples, chemometric methods, such as the partial least squares regression (PLSR) method, the principal component regression (PCR) method, and the multiple linear regression (MLR) method, were used to create separate regression models for sugar and carbohydrates. The predictive power of the regression models was characterized by a coefficient of determination (R²), a root-mean-square error of prediction (RMSEP), and offsets. PLSR was able to accurately model the relationship between the smells of different types of potatoes, sugar, and carbohydrates. The highest and lowest accuracy of models for predicting sugar and carbohydrates was related to Marfona potatoes and Sprite cultivar potatoes. In general, in all cultivars, the accuracy in predicting the amount of carbohydrates was somewhat better than the accuracy in predicting the amount of sugar. Moreover, the linear function had 100% accuracy for training and validation in the C-SVM method for classification of five potato groups. The electronic nose could be used as a fast and non-destructive method for detecting different potato varieties. Researchers in the food industry will find this method extremely useful in selecting the desired product and samples.     

Heterologous Expression and Engineering of the Nitrogenase Cofactor Biosynthesis Scaffold NifEN

NifEN plays a crucial role in the biosynthesis of nitrogenase, catalyzing the final step of cofactor maturation prior to delivering the cofactor to NifDK, the catalytic component of nitrogenase. The difficulty in expressing NifEN, a complex, heteromultimeric metalloprotein sharing structural/functional homology with NifDK, is a major challenge in the heterologous expression of nitrogenase. Herein, we report the expression and engineering of Azotobacter vinelandii NifEN in Escherichia coli. Biochemical and spectroscopic analyses demonstrate the integrity of the heterologously expressed NifEN in composition and functionality and, additionally, the ability of an engineered NifEN variant to mimic NifDK in retaining the matured cofactor at an analogous cofactor‐binding site. This is an important step toward piecing together a viable pathway for the heterologous expression of nitrogenase and identifying variants for the mechanistic investigation of this enzyme.