Characterization of cephalexin loaded nonionic microemulsions

Water/propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/isopropyl myristate/peppermint oil U-type microemulsions were used to solubilize cephalexin. Microemulsion dilution and interfacial factors contributing to the cephalexin solubilization were evaluated. Cephalexin solubilization capacity increases with the increase in the aqueous phase volume fraction (φ) up to 0.4 then decreases. Electrical conductivity of drug loaded and drug free microemulsions increases with φ. The hydrodynamic radius measured by dynamic light scattering of the oil-in-water loaded microemulsions decreases with temperature. The microemulsions were characterized by the volumetric parameters, density, excess volume, ultrasonic velocity and isentropic compressibility. The microemulsion densities increase with φ up to 0.8 then decrease. The excess volume decreases with φ up to 0.8 then stabilizes. Ultrasonic velocities increase with the increase in φ while isentropic compressibility decreases. Analysis of the volumetric parameters enabled the characterization of structural transition along the microemulsion phase region. The presence of water-in-oil, bicontinuous and oil-in-water microemulsions, at aqueous phase volume fractions below 0.2, between 0.3 and 0.7 and above 0.8, respectively were found. Interfacial properties and dynamic structure of the monolayer for drug loaded and drug free microemulsions, were studied by electron paramagnetic resonance spectroscopy employing the nitroxide spin probe 5-doxylstearic acid. The rigidity of the interface was affected by the water content and also the presence of cephalexin.     

Phosphonated fully aromatic polyethers for PEMFCs applications

New homopolymers and copolymers based on aromatic polyethers bearing side diphosphonate and diphosphonic groups have been synthesized. These synthetic efforts resulted in homo and copolymers of high thermal stability but moderate molecular weights. To evaluate the influence of the immobilized phosphonate ester and phosphonic acid moieties on polymer electrolyte membranes for fuel cells applications, blends of the newly synthesized homo and copolymers with a pyridine‐based aromatic polyether were prepared. These blends were miscible with high glass transition temperatures and high thermal stabilities. Furthermore, the introduction of these groups to a polymeric backbone significantly increases the doping ability in phosphoric acid compared to the net matrix as well as the ionic conductivity for high doping levels. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2817–2827, 2010     

Estimating 2‐cycle fixed points of henon map using backpropagation neural networks

The objective of this research is the presentation of a feed‐forward neural network capable of estimating the 2‐cycle fixed points of Henon map by solving their defining nonlinear algebraic system. The network uses the back propagation algorithm and solves the aforementioned system for a set of values of the parameters α and β of Henon map. Besides the estimation of the fixed points, the paper includes the study of the network convergence and its speed for many different initial conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

Fused dihydrofurans from the one-pot,three-component reaction of 1,3-cyclohexanedione,iodobenzene diacetate and alkenes

The one-pot, three-component reactions of substituted 1,3-cyclohexanediones, iodobenzene diacetate and alkenes, under photochemical activation, yields fused dihydrofuran derivatives in good yield via the in situ formation of iodonium ylides.     

Entropy analysis of natural language written texts

The aim of the present work is to investigate the relative contribution of ordered and stochastic components in natural written texts and examine the influence of text category and language on these. To this end, a binary representation of written texts and the generated symbolic sequences are examined by the standard block entropy analysis and the Shannon and Kolmogorov entropies are obtained. It is found that both entropies are sensitive to both language and text category with the text category sensitivity to follow almost the same trends in both languages (English and Greek) considered. The values of these entropies are compared with those of stochastically generated symbolic sequences and the nature of correlations present in this representation of real written texts is identified.     

Modified π-states in ion-irradiated carbon

CVD polycrystalline diamond film, pulse laser-deposited (PLD) carbon film and highly oriented pirolitical graphite (HOPG) as reference, were modified by means of Ar⁺ ion bombardment and characterized by means of Raman scattering, transmission electron microscopy, electron-diffraction (TEM), reflected electron energy loss specroscopy (REELS) and X-ray photoelectron spectroscopy (XPS) techniques. It was found that the diamond was transferred to a carbon with halo-like morphology and disordered stack of graphene segments. Instead of the well-known electron energy loss peak of graphite at 6.5 eV, a new REELS peak appeared at 4-5 eV energies. The observed effect was explained by the modification of π-system in carbon films as a consequence of the formation of non-planar, nanometer-sized graphitic planes.     

Synthesis,conformational analysis and free radical scavenging activity of some new spiropyranoquinolinones

A series of novel spiroadamantyl- and spirocyclical substituted pyranoquinolin-2-ones were synthesized and the conformation of the pyran ring was investigated. The free radical scavenging activity of the synthesized compounds was determined by their interaction with the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). All compounds tested scavenged the DPPH radical and among them derivatives possessing extended conjugation showed the highest activity.     

Plasma transferred arc boriding of a low carbon steel: microstructure and wear properties

Borided coatings on AISI 1018 steel with different boron contents were produced using plasma transferred arc (PTA) melting. The thickness of the coatings ranged from 1 to 1.5 mm and their hardness from 400 to 1600 HV. Hypoeutectic or hypereutectic compositions consisting of primary ferrite or primary Fe₂B borides, respectively, and a eutectic constituent of -Fe+Fe₂B were obtained. The presence of FeB attested in coatings with the highest boron contents seems to be responsible for the intergranular cracks extending from the surface of the coatings to the substrate. Crack free coatings corresponding to the minimum quantity of eutectic and with a minor quantity of FeB were subjected to pin on disk wear testing and compared to the steel of the substrate. It was found that the wear rate of the borided coatings was about four orders of magnitude lower than the wear rate of the steel substrate. A transition from mild to severe wear was observed for the steel substrate material, but it was absent in the case of the borided coatings for the entire range of the applied loads examined. It is shown that the transition in the case of steel occurs when grooving and plastic deformation is replaced by intense cracking of the material above a critical load. In the case of the borided layer the dominant wear mechanism is delamination of the eutectic, however, the platelike borides are able to support the load and remain in the mild wear range for all the loads tested. Both borided and plain steel surfaces have the same friction coefficient after a short transition period, because both develop an oxide layer leading roughly to the same tribosystem with the alumina counterbody.     

A fast algorithm for testing for safety and detecting deadlocks in locked transaction systems

We present an O(n log n log log n) time algorithm which, given a set of n rectangles on the plane with horizontal and vertical sides, and two points s and t, determines whether there exists a monotonically increasing curve from s to t which separates two of the rectangles while avoiding all other rectangles. This solves several problems related to database concurrency control.