Spatial nonlinearity in anisotropic metamaterial plasmonic slot waveguides

We study the main nonlinear solutions of plasmonic slot waveguides made from an anisotropic metamate-rial core with a positive Kerr-type nonlinearity surrounded by two semi-infinite metal regions. First, we demonstrate that for a highly anisotropic diagonal elliptical core, the bifurcation threshold of the asymmetric mode is reduced from GW/m threshold for the isotropic case to 50 MW/m one indicating a strong enhancement of the spatial nonlinear effects, and that the slope of the dispersion curve of the asymmetric mode stays positive, at least near the bifurcation, suggesting a stable mode. Second, we show that for the hyperbolic case there is no physically meaningful asymmetric mode, and that the sign of the effective nonlinearity can become negative

New Heterocyclic Syntheses from Pyridinethiones: an Efficient Route for the Syntheses of Some Novel Azo Derivatives of Thieno[2,3-b]pyridine as Potential Anti-bacterial and Anti-cancer Agents

Derivatives of a heterocyclic system 3-(pyrrol-1-yl)thieno[2,3-b]pyridine 5 and 6 carrying various substituents in the position 2 were synthesized. Some of these products were used to build up a variety of nitrogen- and/or oxygen-containing heterocyclic rings in that position. The electronic configurations of selected products were investigated using the AM1 semi-emperical molecular orbital method. Considerable variations in the magnitude and oriention of the dipole moment were observed. Further, the relative stability of the structures was investigated at physiological conditions via calculation of the electrostaticcomponent of the solvation free energy. The synthesized series showed favourable solvation free energies which were within the range from –30 to –23 kcal/mol.The high polarity and favourable solvation free energychanges at physiological conditions suggest that substitutionin the position 2 could enhance the biological activity of the 3-(pyrrol-1-yl)thieno[2,3-b]pyridine derivatives

Quercetin attenuates, indomethacin-induced acute gastric ulcer in rats

Background: Peptic ulcer diseases are common and are induced by many factors, including stress, smoking, and ingestion of non-steroidal anti-inflammatory drugs. Quercetin is considered to be an anti-oxidant with healing effects on many experimental toxic injuries. The present study aimed to explore the possible effect of quercetin on acute gastric ulcer induced by indomethacin in rats. Materials and methods: Three groups received indomethacin (30 mg/kg body weight) orally by orogastric gavage on two consecutive days. The rats received famotidine (50 mg/kg body weight), quercetin (50 mg/kg body weight), or vehicle alone for 15 consecutive days by oral gavage. The control group received no indomethacin but received vehicle for 15 days by oral gavage. The ulcer index, volume, and pH of gastric juice were measured, and the stomachs were examined by routine light microscopy. Results: Compared with the control group, the indomethacin-treated rats showed a marked damage of the gastric mucosal surface and a high ulcer index. In the famotidine- and quercetin-treated groups, significantly increased antioxidant enzyme activities were observed. The congestion, erosions, and necrosis were reduced with mild inflammatory cell infiltration while no major damage of endothelial cells was observed in the treated rats. Conclusions: The findings of the study show that quercetin had antioxidant effect and can protect gastric mucosa against indomethacin-induced gastric ulceration than famotidine.

Recycling cellular downlink energy for overlay self-sustainable IoT networks

This paper investigates the self-sustainability of an overlay Internet of Things (IoT) network that relies on harvest- ing energy from a downlink cellular network. Using stochastic geometry and queueing theory, we develop a spatiotemporal model to derive the steady state distribution of the number of packets in the bu ff ers and energy levels in the batteries of IoT devices given that the IoT and cellular communications are allocated disjoint spectrum. Particularly, each IoT device is modeled via a two-dimensional discrete-time Markov Chain (DTMC) that jointly tracks the evolution of data bu ff er and energy battery. In this context, stochastic geometry is used to derive the energy generation at the batteries and the packet transmission probability from bu ff ers taking into account the mutual interference from other active IoT devices. To this end, we show the Pareto-Frontiers of the sustainability region, which defines the network parameters that ensure stable network operation and finite packet delay. The results provide several insights to design self-sustainable IoT networks. Index Terms —Spatiotemporal models, stochastic geometry, queuing theory, energy harvesting, packet transmission success probability, two-dimensional discrete-time Markov chain, sta- bility conditions

The physical determinants of the DNA conformational landscape: an analysis of the potential energy surface of single-strand dinucleotides in the conformational space of duplex DNA

A multivariate analysis of the backbone and sugar torsion angles of dinucleotide fragments was used to construct a 3D principal conformational subspace (PCS) of DNA duplex crystal structures. The potential energy surface (PES) within the PCS was mapped for a single-strand dinucleotide model using an empirical energy function. The low energy regions of the surface encompass known DNA forms and also identify previously unclassified conformers. The physical determinants of the conformational landscape are found to be predominantly steric interactions within the dinucleotide backbone, with medium-dependent backbone-base electrostatic interactions serving to tune the relative stability of the different local energy minima. The fidelity of the PES to duplex DNA properties is validated through a correspondence to the conformational distribution of duplex DNA crystal structures and the reproduction of observed sequence specific propensities for the formation of A-form DNA. The utility of the PES is demonstrated through its succinct and accurate description of complex conformational processes in simulations of duplex DNA. The study suggests that stereochemical considerations of the nucleic acid backbone play a role in determining conformational preferences of DNA which is analogous to the role of local steric interactions in determining polypeptide secondary structure