Extending the dynamic range of an energy harvester using nonlinear damping

This paper introduces the use of nonlinear damping for extending the dynamic range of vibration energy harvesters. A cubic nonlinear damper is initially considered and the average harvested power and the throw are obtained for different sinusoidal base excitation amplitudes and frequencies, both numerically and analytically. It is demonstrated that when excited at resonance, at an amplitude below its maximum operational limit, the harvested power using a nonlinear damper can be significantly larger than that of a linear energy harvester, therefore expanding its dynamic range. A potential approach to implementing cubic nonlinearity using a shunted electromagnetic device is also presented.     

Ylide stabilized carbenes: a computational study

High‐level Density Functional Theory calculations, coupled with appropriate isodesmic reaction, are employed to investigate the effects of α‐carbon, ammonium, phosphorus, and sulfur ylides, cyclization, and unsaturation on the stability, multiplicity, and reactivity of novel singlet (S) and triplet (T) carbenes. Among them the highly π‐donating α‐ammonium ylide is found to exert the highest stabilizing effect on the carbenic center. α‐Ammonium ylides resist dimerization and hydrogenation. They show wider singlet–triplet energy gap (ΔΕ_S–T), broader band gap (ΔΕ_HOMO–LUMO), and higher nucleophilicity compared to the reported stable N‐heterocyclic carbenes. Aromatic cyclic unsaturated ammonium, phosphorus, and sulfur ylide carbenes appear more stable than their saturated cyclic analogs which are in turn more viable than their acyclic counterparts. Copyright © 2014 John Wiley & Sons, Ltd.     

Entanglement dynamics of a strongly driven trapped atom

We study the entanglement between the internal electronic and the external vibrational degrees of freedom of a trapped atom which is driven by two lasers into electromagnetically induced transparency. It is shown that basic features of the intricate entanglement dynamics can be traced to Landau-Zener splittings (avoided crossings) in the spectrum of the atom-laser field Hamiltonian. We further construct an effective Hamiltonian that describes the behavior of entanglement under dissipation induced by spontaneous emission processes. The proposed approach is applicable to a broad range of scenarios for the control of entanglement between electronic and translational degrees of freedom of trapped atoms through suitable laser fields.     

Surface properties of polypropylene/organoclay nanocomposites

Influence of nanoclay amount on surface properties of the nanocomposites was investigated using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), contact angle measurement, scanning electron microscopy (SEM) and transmission spectroscopy (TS). Polypropylene based nanocomposites containing various loads of nanoclay were prepared by melt compounding. X-ray diffraction (XRD) characterized the dispersion of nanoclay in polymer matrix. AFM and SEM studies have shown increase in surface roughness by raising the amount of nanoclay. Contact angle measurements of the resultant nanocomposites have also shown improvement in wettability related to disperse part of surface tension. POM images illustrated an increase in the number of spherulite simultaneously with a decrease in their size; this result was also supported by differential scanning calorimetry (DSC).     

New way to produce dense double-antikaonic dibaryon system, KKNN, through Λ(1405)-doorway sticking in p+p collisions

A recent successful observation of a dense and deeply bound K nuclear system, K-pp, in the p+p→K++K-pp reaction in a DISTO experiment indicates that the double-K dibaryon, K-K-pp, which was predicted to be a dense nuclear system, can also be formed in p+p collisions. We find theoretically that the K--K- repulsion plays no significant role in reducing the density and binding energy of K-K-pp and that, when two Λ(1405) resonances are produced simultaneously in a short-range p+p collision, they act as doorways to copious formation of K-K-pp, if and only if K-K-pp is a dense object, as predicted.     

Three‐component synthesis of spiro[indoline‐3,5′‐pyrimido[4,5‐b]quinoline]‐triones in water

A one‐pot, three‐component method for the efficient and simple synthesis of novel 2′‐amino‐8′,9′‐dihydro‐3′H‐spiro[indoline‐3,5′‐pyrimido[4,5‐b]quinoline]‐2,4′,6′(7′H,10′H)‐trione derivatives in aqueous media is reported. J. Heterocyclic Chem., (2011).     

Preparation of Silica‐bonded Propyl‐diethylene‐triamine‐N‐sulfamic Acid as a Recyclable Catalyst for Chemoselective Synthesis of 1,1‐Diacetates

A simple and efficient procedure for the preparation of silica‐bonded propyl‐diethylene‐triamine‐N‐sulfamic acid (SPDTSA) by reaction of 3‐diethylenetriamine‐propylsilica (DTPS) and chlorosulfonic acid in chloroform is described. Silica‐bonded propyl‐diethylene‐triamine‐N‐sulfamic acid is employed as a recyclable catalyst for the synthesis of 1,1‐diacetates from aromatic aldehydes and acetic anhydride under mild and solvent‐free conditions at room temperature. Catalyst could be recycled for several times without any additional treatment.     

Developing a Nano‐Biosensor for DNA Hybridization Using a New Electroactive Label

Development of electrochemical DNA hybridization biosensors based on carbon paste electrode (CPE) and gold nanoparticle modified carbon paste electrode (NGMCPE) as transducers and ethyl green (EG) as a new electroactive label is described. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were applied for the investigation and comparison of bare CPE and NGMCPE surfaces. Our voltammetric and spectroscopic studies showed gold nanoparticles are enable to facilitate electron transfer between the accumulated label on DNA probe modified electrode and electrode surface and enhance the electrical signals and lead to an improved detection limit. The immobilization of a 15‐mer single strand oligonucleotide probe on the working electrodes and hybridization event between the probe and its complementary sequence as a target were investigated by differential pulse voltammetry (DPV) responses of the EG accumulated on the electrodes. The effects of some experimental variables on the performance of the biosensors were investigated and optimum conditions were suggested. The selectivity of the biosensors was studied using some non‐complementary oligonucleotides. Finally the detection limits were calculated as 1.35×10^?10 mol/L and 5.16×10^?11 mol/L on the CPE and NEGCPE, respectively. In addition, the biosensors exhibited a good selectivity, reproducibility and stability for the determination of DNA sequences.     

CuO nanoparticles: An efficient and recyclable nanocatalyst for the rapid and green synthesis of 3,4-dihydropyrano[c]chromenes

Copper oxide nanoparticles showed excellent catalytic activity through three-component condensation reaction of aldehydes, malononitrile, and 4-hydroxycoumarin for the synthesis of 3,4-dihyropyrano[c]chromenes in water medium in excellent yields and very short reaction times.     

Enhanced Production of Citric Acid in Yarrowia lipolytica by Triton X-100

Various chemical surfactants could affect permeability of yeast cells. In this study, effects of the surfactant addition upon yeast cells permeability and citric acid (CA) production by Yarrowia lipolytica strains DSM 3286 and M7 were investigated. The addition of Triton X-100 increased 1.4-1.8-fold of the maximum CA quantity achieved for both strains, with final CA concentrations ranging between 75-85 g/l that correspond to CA conversion yields per unit of glucose consumed of ~0.80-0.84 g/g. Scanning electron micrographs of yeast cells showed that the cells treated with Triton X-100 had altered cell structure and were smaller and narrower compared with the non-treated ones. The results showed that Triton X-100 could be used in order to increase the efficiency of CA production by Y. lipolytica strains.