Calculation of effective index for different dielectric waveguides structures made of PVCi/PMATRIFE polymers at telecom-wavelength \lambda =1.55\,\upmu m

In this paper, a number of polymeric waveguide structures have been analyzed by using two distinct techniques which are: effective index method (EIM) and numerical simulation based on finite difference method (FDM). The main aim of this investigation is the calculation of effective indexes (EI) of the following structures: rib, ridge and buried channel waveguides at telecom wavelength $\lambda =1.55\,\upmu \hbox {m}$ for different dimensions of waveguide cores varying from 1.5–4  $\upmu \hbox {m}$ . Moreover, other optical propagation characteristics such as: confinement factor, normalized and propagation constant have been studied in TE polarisation. Otherwise the effect of the structure parameters and dimensions on the dispersion characteristics has been investigated. On the other hand, the optical field distribution has been computed using commercial software named OlympIOs. The polymers applied in the design of waveguide structures are the PVCi (n = 1,562 $\lambda = {1.55}\,\upmu $ m) used as core layer and the PMATRIFE (n = 1,409 $\lambda = 1.55\,\upmu $ m) used as substrate or cladding layer. The results obtained using EIM and simulation based on FDM show that effective index and field confinement factor of TE fundamental mode increase monotonously with the increasing dimension of core. The obtained results are in good agreement with published data based on other numerical methods.     

Three new flavonoid glycosides, byzantionoside B 6'-O-sulfate and xyloglucoside of (Z)-hex-3-en-1-ol from Ruellia patula

Three new flavonoid glycosides, demethoxycentaureidin 7-O-β-D-galacturonopyranoside, pectolinarigenin 7-O-α-L-rhamnopyranosyl-(1?→4″)-β-D-glucopyranoside and 7-O-α-L-rhamnopyranosyl-(1?→4″)-β-D-glucuronopyranoside, a new megastigmane glucoside, byzantionoside B 6'-O-sulfate, and a new (Z)-hex-3-en-1-ol O-β-D-xylopyranosyl-(1″→2')-β-D-glucopyranoside, were isolated from leaves of Ruellia patula JACQ., together with 12 known compounds, β-sitosterol glucoside, vanilloside, bioside (decaffeoyl verbascoside), acteoside (verbascoside), syringin, benzyl alcohol O-β-D-xylopyranosyl-(1″→2')-β-D-glucopyranoside, cistanoside E, roseoside, phenethyl alcohol O-β-D-xylopyranosyl-(1″→2')-β-D-glucopyranoside, (+)-lyoniresinol 3α-O-β-D-glucopyranoside, isoacteoside and 3,4,5-trimethoxyphenol O-α-L-rhamnopyranosyl-(1″→6')-β-D-glucopyranoside. Their structures were elucidated by means of spectroscopic analyses.     

Application of Crosslinked Ionic Poly(Vinyl Alcohol) Nanogel as Adsorbents for Water Treatment

Core-shell smart ionic nanogels based on poly(vinyl alcohol) (PVA) core and poly(N-isopropylacrylamide/acrylic acid) p(NIPAm-AAc) shell particles were successfully synthesized through a one-step surfactant-free emulsion polymerization method (SFEP). Different mole ratios of p(NIPAm-AAc) shells were synthesized. The morphologies of PVA/p(NIPAm-AAc) nanogels were investigated by transmission electron microscope (TEM). The data showed the formation of spherical nanoparticles and well-defined core-shell nanogels. PVA/p(NIPAm-AAc) core-shell nanogels were applied as a novel polymeric adsorbent to remove heavy metal pollutants from aqueous solution. Copper(II) (Cu²⁺) ions were selected as the target pollutant to evaluate these nanoparticles’ adsorption capability. The influence of the uptake conditions such as pH, weight ratio of nanoparticles, time, initial feed concentration, and adsorption temperature on the metal ion binding capacity of nanogels was also tested. Adsorption equilibrium data were calculated according to Langmuir and Freundlich isotherms. It was found that the sorption of Cu²⁺ was better suited to the Freundlich adsorption model than the Langmuir adsorption model. Also, the selectivity of the nanogels toward the different metal ions such lead (Pb²⁺) and cadmium (Cd²⁺) were tested. The maximum of Cu²⁺ ions adsorbed on to PVA/p(NIPAm-AAc) core-shell nanogels adsorbent was 94 mg/g obtained under simple and fast experimental conditions, indicating these nanogels can be used as effective and practical polymeric adsorbents.     

Swelling Behavior of pH-Sensitive Copolymers Containing 2-Acrylamido-2-Methyl Propane Sulfonic Acid and Acrylic Acid Crosslinked with Vinyl Trimethoxy Silane Crosslinker

Copolymers of 2-acrylamido-2-methyl propane sulfonic acid and acrylic acid were crosslinked in the presence of different mol% of either vinyl trimethoxy silane (VTMS) as the crosslinking agent under acidic conditions or N,N-methylenebisacrylamide (MBA) as crosslinker using solution radical polymerization. The resultant xerogels were characterized by extracting the soluble fractions and measuring the equilibrium water content. Soluble fractions of the crosslinked networks were reduced by varying the MBA and VTMS concentrations. The surface morphology of the crosslinked polymers was observed by scanning electron microscope. The influence of pH on the swelling behavior of gels was investigated. The swelling behaviors of the resulting gels show pH sensitivity.     

CONCERNING THE ORIGIN OF CHARGE AT THE POLYSTYRENE PARTICLE/WATER INTERFACE

The electrophoretic mobility behavior of well-characterized polystyrene latex particles, carrying one type of surface functional endgroups, has been studied as a function of pH. At low pH, the interaction of protons with the functional endgroups increased in the order: Hydroxyl > carboxyl > sulfate; at high pH the order of interaction was reversed; and at intermediate pH no interactions were observed. The particles of the polystyrene latexes in their different forms at the intermediate pH range, dispersed in deionized water, all exhibited the same mobility irrespective of the functional endgroup. The origin of charge in these systems is explained as being the result of either the preferential adsorption of hydroxyl ions or an electron - injection mechanism due to the overlap of local intrinsic molecular - ion states in polystyrene and water. At low concentrations of functional endgroups, the surface properties of the polystyrene latexes are largely dependent upon the hydrophobic nature of the surface.     

Novel di-μ-chloro-bis[chloro(4,7-dimethyl-1,10-phenanthroline)cadmium(II)] dimer complex: synthesis, spectral, thermal, and crystal structure studies

A novel di-μ-chloro-bis[chloro(4,7-dimethyl-1,10-phenanthroline)cadmium(II)] dimer complex has been prepared by reacting CdCl₂·2.5H₂O with 4,7-dimethyl-1,10-phenanthroline (dmphen) ligand. The complex was characterized on the basis of elemental analysis, FAB-MS, IR, UV–visible, ¹H, and ¹³C NMR spectroscopy, TG/DTA, and X-ray single-crystal diffraction studies. The Cd(II) ions in [CdCl₂(C₁₄H₁₂N₂)]₂ are coordinated to three Cl atoms with the centrosymmetric dimer bridged through the Cl atoms and two N atoms in a slightly distorted square-pyramidal disposition. Several hydrogen bonds formed between the terminal Cl atoms and H-Me/H-Ph groups may stabilize the structure in the dimer form.     

Experimental determination and prediction of (solid + liquid) phase equilibria for binary mixtures of aromatic and fatty acids methyl esters

Solid–liquid equilibria for binary mixtures of {methyl stearate (1) + biphenyl (2)}, {methyl stearate (1) + naphthalene (2)}, {methyl palmitate (1) + biphenyl (2)} and {methyl palmitate (1) + naphthalene (2)} were measured using differential scanning calorimeter. Simple eutectic behaviours for these systems were observed. The experimental results were correlated by means of the NRTL, Wilson, UNIQUAC and ideal models. The root-mean-square deviations of the solubility temperatures for all measured data vary from 0.5477 K (for UNIQUAC model) to 7.79 K; the deviations depend on the binary system studied and particular model used. The best solubility correlation was obtained with UNIQUAC model and this observation confirms previous results.     

Electrodeposition of nanocrystalline Ni–Cu alloy from environmentally friendly lactate bath

A new environmentally friendly electroplating bath for Ni–Cu alloy deposition was developed. Lactic acid was used as a complexing agent. The influence of bath composition, current density, pH and temperature on cathodic polarization, cathodic current efficiency and alloy composition was studied. Different proportions of the two metals were obtained by using different deposition parameters, but at all [Ni²⁺] / [Cu²⁺] ratios studied, preferential deposition of Cu occurred and regular co‐deposition took place. The Ni content of the deposit increased with Ni²⁺ content and current density and decreased with temperature. The surface morphology of the deposited Ni–Cu alloy was investigated using scanning electron microscopy. The crystal structure was examined using the X‐ray diffraction technique. The results showed that the deposits consisted of a single solid solution phase with a face‐centered cubic structure. The crystallite size lies in the range of 12 to 25 nm for as‐plated alloys. Copyright © 2014 John Wiley & Sons, Ltd.     

Sonochemical and sonocatalytic degradation of monolinuron in water

The degradation of the phenylurea monolinuron (MLN) by ultrasound irradiation alone and in the presence of TiO(2) was investigated in aqueous solution. The experiments were carried out at low and high frequency (20 and 800 kHz) in complete darkness. The degradation of MLN by ultrasounds occurred mainly by a radical pathway, as shown the inhibitory effect of adding tert-butanol and bicarbonate ions to scavenge hydroxyl radicals. However, CO(3)(-) radicals were formed with bicarbonate and reacted in turn with MLN. In this study, the degradation rate of MLN and the rate constant of H(2)O(2) formation were used to evaluate the oxidative sonochemical efficiency. It was shown that ultrasound efficiency was improved in the presence of nanoparticles of TiO(2) and SiO(2) only at 20 kHz. These particles provide nucleation sites for cavitation bubbles at their surface, leading to an increase in the number of bubbles when the liquid is irradiated by ultrasound, thereby enhancing sonochemical reaction yield. In the case of TiO(2), sonochemical efficiency was found to be greater than with SiO(2) for the same mass introduced. In addition to the increase in the number of cavitation bubbles, activated species may be formed at the TiO(2) surface that promote the formation of H(2)O(2) and the decomposition of MLN.