Superposition of Laser Light Beams Coupled to Vacuum Reservoir

Journal of Russian Laser Research - In this paper, we study the statistical and squeezing properties of the cavity light produced by a degenerate three-level laser, in view of the solution of the...     

Amperometric determination of hydrogen peroxide with a manganese dioxide film-modified screen printed carbon electrode

A carbon thick film electrode modified with an MnO₂-film is investigated as an amperometric detector for hydrogen peroxide in flow-injection analysis (FIA). At an operating potential of +0.48 V vs. Ag/AgCl catalytic oxidation of the analyte is exploited for amperometric monitoring. Experimental parameters, such as pH of the carrier, working potential, flow rate and injection volume, are optimized. The amperometric signals are linearly proportional to the concentration of H₂O₂ in the range from 0.005 to 10 mg/L, showing a detection limit (3σ) of 2.3 μg/L. The method is applied to the determination of H₂O₂ in rain water and to a simple assay to quantify glucose in human plasma.     

Synthesis of some N-[pyridyl(phenyl)carbonylamino]hydroxyalkyl-(benzyl)-1,2,3,6-tetrahydropyridines as potential anti-inflammatory agents

1,2,3,6-Tetrahydropyridines are known to possess analgesic, anti-inflammatory, hyperglycemic and hypoglycemic activities. Substituted 2,4-dinitrophenylpyridinium chlorides 3 were formed by reacting 1-chloro-2,4-dinitrobenzene with hydroxypropyl, hydroxymethyl and benzyl substituted pyridines 2 . Attack of the pyridinium chlorides 3 with pyridylcarbonyl hydrazides or benzoyl hydrazides 4 gave the isolable 2,4-dinitroanilino derivative 5 which underwent hydrolysis when refluxed in water:p-dioxane mixture (1:4 v/v) to afford the pyridinium ylides 6 . Sodium borohydride reduction of 6 in absolute ethanol at 0° for 4–6 hours resulted in the isolation of the 1,2,3,6-tetrahydropyridines 7 in good yields.     

Synthesis of some N-[pyridyl(phenyl)carbonylamino]-alkyl-1,2,3,6-tetrahydropyridines

Alkyl substituted 2,4-dinitrophenylpyridinium chlorides 3 are formed by the nucleophilic substitution of 1-chloro-2,4-dinitrobenzene with alkyl pyridines. Reaction of pyridyl acid hydrazides or benzoyl hydrazides 4 with the pyridinium chlorides 3 furnish the isolable 2,4-dinitroanilino derivatives 5 which undergo hydrolysis when refluxed in water:p-dioxane mixture (1:4 v/v) to yield the pyridinium ylides 6 . Sodium borohydride reduction of 6 in absolute ethanol at 0° for 4 hours result the formation of the title compounds 7 in moderate to excellent yields.     

Development and validation of HPLC method for the resolution of drug intermediates: DL-3-Phenyllactic acid, DL-O-acetyl-3-phenyllactic acid and (+/-)-mexiletine acetamide enantiomers

Sensitive and specific, high-performance liquid chromatography (HPLC) methods have been developed and validated for linearity, accuracy and precision for the quantification of dl-3-phenyllactic acid, dl-O-acetyl-3-phenyllactic acid and (+/-)-mexiletine acetamide enantiomers. Chromatographic separations were performed on a Chiralcel OJ-H column (0.46 mm x 250 mm, 5 microm, Daicel Chemical Industries, Japan) based on cellulose tris-(4-methyl benzoate) chiral stationary phase. The mobile phase consists of hexane and isopropanol (IPA) in the ratio of 90:10 containing 0.1% trifluoroacetic acid (in case of dl-3-phenyllactic acid and dl-O-acetyl-3-phenyllactic acid) and hexane and IPA (95:5) containing 0.1% triethylamine (in case of (+/-)-mexiletine acetamide) and the flow rate was set at 0.5 ml/min at 25 degrees C. The detection was carried out at 261 nm for dl-3-phenyllactic acid and dl-O-acetyl-3-phenyllactic acid and at 254 nm for (+/-)-mexiletine acetamide. The developed methods were utilized for monitoring the progress of lipase catalyzed enantioselective synthesis of O-acetyl-3-phenyllactic acid and mexiletine acetamide from dl-3-phenyllactic acid and (+/-)-mexiletine, respectively.     

Statistical Properties of Nondegenerate Three-Level Laser

Journal of Russian Laser Research - We study the squeezing and statistical properties of the light produced by nondegenerate three-level lasers coupled to a vacuum reservoir, in which two different...     

Modelling of the impedimetric responses of an aflatoxin B1 immunosensor prepared on an electrosynthetic polyaniline platform

Aflatoxins are a group of mycotoxins that have deleterious effects on humans and are produced during fungal infection of plants or plant products. An electrochemical immunosensor for the determination of aflatoxin B₁ (AFB₁) was developed with AFB₁antibody (AFB₁-Ab) immobilized on Pt electrodes modified with polyaniline (PANi) and polystyrene sulphonic acid (PSSA). Impedimetric analysis shows that the electron transfer resistances of the Pt/PANi–PSSA electrode, the Pt/PANi–PSSA/AFB₁-Ab immunosensor and Pt/PANi–PSSA/AFB₁-Ab incubated in bovine serum albumin (BSA) were 0.458, 720 and 1,066 kΩ, respectively. These results indicate that electrochemical impedance spectroscopy (EIS) is a suitable method for monitoring the change in electron transfer resistance associated with the immobilization of the antibody. Modelling of EIS data gave equivalent circuits which showed that the electron transfer resistance increased from 0.458 kΩ for the Pt/PANi–PSSA electrode to 1,066 kΩ for the Pt/PANi–PSSA/AFB₁-Ab immunosensor, indicating that immobilization of the antibody and incubation in BSA introduced an electron transfer barrier. The AFB₁ immunosensor had a detection limit of 0.1 mg/L and a sensitivity of 869.6 kΩ L/mg.     

Transient Behavior in Variable Geometry Industrial Gas Turbines: A Comprehensive Overview of Pertinent Modeling Techniques

Generally, industrial gas turbines (IGT) face transient behavior during start-up, load change, shutdown and variations in ambient conditions. These transient conditions shift engine thermal equilibrium from one steady state to another steady state. In turn, various aero-thermal and mechanical stresses are developed that are adverse for engine’s reliability, availability, and overall health. The transient behavior needs to be accurately predicted since it is highly related to low cycle fatigue and early failures, especially in the hot regions of the gas turbine. In the present paper, several critical aspects related to transient behavior and its modeling are reviewed and studied from the point of view of identifying potential research gaps within the context of fault detection and diagnostics (FDD) under dynamic conditions. Among the considered topics are, (i) general transient regimes and pertinent model formulation techniques, (ii) control mechanism for part-load operation, (iii) developing a database of variable geometry inlet guide vanes (VIGVs) and variable bleed valves (VBVs) schedules along with selection framework, and (iv) data compilation of shaft’s polar moment of inertia for different types of engine’s configurations. This comprehensive literature document, considering all the aspects of transient behavior and its associated modeling techniques will serve as an anchor point for the future researchers, gas turbine operators and design engineers for effective prognostics, FDD and predictive condition monitoring for variable geometry IGT.     

Germanium films with strong in-plane and out-of-plane texture on flexible,randomly textured metal substrates

High efficiencies have been achieved in photovoltaic cells based on III–V compounds grown on single crystal germanium substrates. Since the size of these substrates is limited and their cost is very high, such III–V photovoltaics have not found widespread terrestrial use. The objective of this work is to develop highly textured, epitaxial germanium thin films on inexpensive substrates suitable for roll-to-roll continuous processing to serve as templates for III–V compounds. Germanium films with a high degree of in-plane and out-of plane texture have been demonstrated on randomly textured, flexible nickel alloy substrates by epitaxial growth on template films made by ion beam-assisted deposition (IBAD). In order to achieve epitaxial growth, an intermediate layer of CeO₂ was found to be required between the IBAD MgO template and the Ge film. Our study shows that structural match between Ge and the underlying oxide layer is the key to epitaxial growth. Room temperature optical bandgap of the Ge films was identified at 0.67 eV suggesting minimal residual strain in the film. Refraction index and extinction coefficient values of the epitaxial Ge film were found to match well with that measured from a reference Ge single crystal.     

Layer-by-layer assembly and electrically controlled disassembly of water-soluble Poly(3,4-ethylenedioxythiophene) derivatives for bioelectronic interface

Poly(3,4-ethylenedioxythiophene (PEDOT) derivatives display a multitude of attractive properties such as high conductivity, biocompatibility, ease of functionalization, and high thermal stability. As a result, they show promise for applications in materials and biomedical engineering. In order to increase their applications in the practical domain, trivial fabrication techniques are required. Here, we present a simple layer-by-layer dip methodology to assemble water-soluble PEDOT derivatives that can then be disassembled via electrical stimulation. As a result, a dynamic PEDOT layered system is fabricated and could be applied as responsive materials for bioengineering. PEDOT-SO₃ and PEDOT-NMe₃ are synthesized via direct C-H arylation polymerization and chemical polymerization, respectively. The electrostatic interactions between oppositely charged SO₃⁻ and NMe₃⁺ enabled the stacking of PEDOT derivatives. The layer-by-layer assemblies are confirmed by ultraviolet–visible spectroscopy and profilometer. Morphological analyses are performed using scanning electron microscopy and atomic force microscopy, which revealed that the polymer coatings are uniform without any cracks. In situ material assembly is studied using quartz crystal microbalance, and we also demonstrate that these PEDOT-derivative assemblies can be disintegrated by electrical stimulation. Cyclic voltammetry shows a proportional increase in stored charge density with the increase in bilayer thickness, confirming stable electroactivity of these assemblies. Using this approach, we can assemble conductive bio interface on both conductive and nonconductive surfaces, expanding the capability to fabricate bioelectronic electrodes.