Diethylmethyl chitosan as an antimicrobial agent: Synthesis, characterization and antibacterial effects

Chitosan with excellent biodegradable and biocompatible characteristics has received attention as an oral drug delivery vehicle. A quaternized chitosan (i.e., N-diethylmethyl chitosan, DEMC) was prepared based on a modified two-step process via a 2² factorial design to optimize the preparative conditions. DEMC was fully characterized using FTIR and ¹H-NMR spectroscopies. As calculated using NMR-based data, high degree of quaternization was achieved through the optimized two-step process. The highly quaternized biopolymeric derivative was subjected to microbial experiments. The antimicrobial activities of chitosan and DEMC against Escherchia coli were compared by calculation of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Our data indicates that although the antimicrobial activity of DEMC is higher than that of chitosan in acetic acid medium, the both compounds are pH dependent and an increase in concentration of acetic acid results in a significant decrease in both MIC and MBC.     

Asymmetric coherent photon tunneling filter in an optical waveguide structure

Based on the well-known electron coherent tunneling phenomenon, by simulation, a photonic tunneling filter fabricated in an optical waveguide is proposed. The Bragg grating structure is applied as the photonic barrier. Two photonic barriers confine a coherent resonance cavity or photon-quantum-well. We report an asymmetric-barrier structure with opposite phase. In this configuration, the central tunneling wavelength is exactly the same as the Bragg wavelength of the grating, independent of the photon-quantum-well dimension. The photon-quantum-well length can be adjusted to make the tunneling peak interval fall to a desired spacing. The photon barrier length is responsible for the filter bandwidth. As an application, an asymmetric grating photon tunneling filter with International Telecommunication Union grid is demonstrated.     

BTZ Black Hole in Non-Commutative Spaces

In this letter we compute the corrections to the horizons, the horizon area and Hawking temperature of a BTZ black hole. These corrections stem from the space non-commutativity. We show that in non-commutative case, non-rotating BTZ black hole in contrast with commutative case has two horizons.     

Scanning Kelvin nanoprobe detection in materials science and biochemical analysis

The Kelvin nanoprobe is an extremely sensitive instrument capable of discerning subtle molecular interactions using vibrating electromagnetic and acoustic fields. It is based on the measurement of a fundamental material property, the work function. Modulation of this substrate parameter is caused by the adsorption or desorption of molecules, oxidation, corrosion, contamination, mechanical stress, illumination, temperature changes, electrostatic charging, surface treatment, attached dipolar structures and/or the immobilization of biomolecules. The present article explains the general principles of the method and offers an indication of the wide range of possible applications, with an emphasis on potential use in the biotechnological arena.     

Mode locking a 1550 nm semiconductor disk laser by using a GaInNAs saturable absorber

Passive mode locking of an optically pumped, InP-based, 1550 nm semiconductor disk laser by using a GaInNAs saturable absorber mirror is demonstrated. To reduce material heating and enable high-power operation, a 50 microm thick diamond heat spreader is bonded to the surface of the gain chip. The laser operates at a repetition frequency of 2.97 GHz and emits near-transform-limited 3.2 ps pulses with an average output power of 120 mW.     

Synthesis of 6-acylmethylphenanthridine enaminones

A series of 6-acylmethylphenanthridine derivatives were synthesized by reaction of aliphatic and aromatic esters with 6-methylphenanthridine in the presence of phenyllithium. Enaminone form of the obtained compounds was investigated by spectroscopic methods. The results revealed that the presence of aromatic rings on 3- and 4-position of 2-acylmethylquinolines (6-acylmethylphenanthridines) is the most important factor for the preference of the enaminone form b. It was found that the intramolecular hydrogen bonding is the only factor that can damage aromaticity of the phenanthridine moiety.     

Calculation of η′ Decay Modes Using Chiral Perturbation Theory

In this paper, with the use of Chiral Perturbation theory (χPT), we have studied the η′ decays in to 3π and 2πη, after performing these reactions. The Scattering amplitude and decay width are calculated for different modes up to NLO. The Dalitz plot expansion and parameter fixing for each of them is also calculated. Experimental results are in good agreement with the obtained results. We compare our results with charged and neutral decay parameters with the most recent Particle Data Group results of these observables. At next-to-leading order, our results for decay widths of the charged (neutral) channel are Γ(η′→2πη)=83.6±0.8 (43.0±2.2) keV and Γ(η′→3π)=0.716±0.072 (0.320±0.079) keV. These results are in agreement with several other theoretical determinations and experimental findings.