Computer simulation of the propagation of extremely short femtosecond pulse in single-mode fiber with shifted dispersion characteristics

We present the results of theoretical study of generation of spectral supercontinuum by an extremely short femtosecond laser pulse with the central wavelength corresponding to zero dispersion, propagating in a single-mode fiber with shifted dispersion characteristics. High-order nonlinear Schrödinger equation (HONSE) is considered with higher-order terms taken into account. Numerical integration of HONSE is performed by the method of lines. Time dependence of instantaneous frequencies of the femtosecond pulse is obtained. The evolution of the pulse spectrum is calculated and the medium length dependence of the spectrum width is obtained. For study of the time-frequency dynamics of extremely short femtosecond laser pulse propagating in single-mode optical fiber with allowance for higher order terms, the Wigner transformation (WT) was used.     

Encapsulation of indomethacin using coaxial ultrasonic atomization followed by solvent evaporation

We have encapsulated indomethacin into poly (lactide-co-glycolide) (PLGA) using coaxial ultrasonic atomization technique. The specific aims of this study were to evaluate the effect of drug loading and a change in relative concentration of polymer in the inner and outer layers of coflowing spray liquids on the physicochemical characteristics of the particles. Indomethacin, a non steroidal anti-inflammatory drug, was selected as a model compound. The micro/nanocapsules prepared using a drug free PLGA solution as an outer layer showed higher encapsulation efficiency. Thermal analysis of the formulations indicated that indomethacin was dissolved within the PLGA matrix. The formulations prepared with 25mg indomethacin showed relatively smaller particle size compared with the formulations prepared with 50 mg indomethacin. The particles, in general, showed bi- and tri-modal distribution. Irrespective of the compositions of the liquids 1 and 2, all the particles were smooth and spherical. A cross-section view of the particles revealed the presence of three different internal morphologies. These formulations were a mixture of hollow or solid spheres, and single or multiple spheres encapsulated into a larger sphere. To the best of our knowledge, this is the first study revealing the cross-sectional view of particles prepared with coaxial ultrasonic atomization technique.     

Sexual behavior of university students in the Arab Near East.

"In order to obtain data on sex practices and beliefs of male university students in the Arab Near East, and to compare them with data from American universities, a questionnaire was administered to 113 students at the American University of Beirut, Lebanon, under conditions designed to insure anonymity and cooperation." Data on nocturnal emissions, masturbation, homosexual intercourse, and heterosexual intercourse are discussed. An attempt is made to relate the data to known elements of the culture of this area. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polyaniline dispersions. 3. Influence of the polymerization conditions

Several series of polyaniline dispersions were prepared by oxidative polymerization of aniline in aqueous medium. Ammonium persulfate was used as an oxidizing agent and poly(vinyl alcohol) as a steric stabilizer of dispersions. The amount of dispersion particles their size and uniformity and the fraction of the steric stabilizer attached to the particles were determined in dependence on the concentration of the individual components and on temperature. The properties of resulting dispersions are controlled mainly by the concentration of the oxidizing agent and by the polyaniline/stabilizer ratio.     

Copolymers of aniline and o‐methoxyaniline. II. Thermoanalytical studies

A study on the thermal stability, thermodynamical parameters, especially relaxation transition temperature (T_g), and their change upon irreversible reactions (crosslinking, postpolymerization, decomposition, etc.) taking place on heating of the undoped homo‐ and copolymers of aniline and o‐methoxyaniline was performed by using differential scanning calorimetry. It was found that polyaniline and its oligomers might be responsible for the postpolymerization process observed on heating thermograms of the polymers in their emeraldine base form. It can be stated that the proceeding of this process appears to be a reason for the higher thermal stability of polyaniline when compared with poly(o‐methoxyaniline). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2729–2734, 2007     

Roasting of the sulfide-zinc concentrate with predominant obtaining of sulfate roast for effective leaching

Roasting the sulfide-zinc concentrate with a high silver content is investigated by thermogravimetric and differential thermal analyses in the mode of polythermal heating. It is shown that roasting at 630 ± 10°C makes it possible to obtain mostly sulfate roast, which is most suitable for the effective recovery of zinc and other components.     

On the stability and in situ epoxidation of natural rubber in latex by performic acid

The aggregative stability of natural rubber (NR) latex stabilized by nonionic, fatty alcohol ethylene oxide condensate surfactant (Verol S-15) was studied in the presence of formic acid. Natural rubber latex having an additional 3–5 phr surfactant is stable at pH 2 when acidified by formic acid and can be successfully subjected to the subsequent in situ epoxidation. Using a large ratio of H₂O₂ to isoprene unit (0.4–4.0 M/M) and large excess of H₂O₂ to HCOOH (3–13 M/M) in reaction, the in situ epoxidation can be performed with reaction mixture having dry rubber content up to 35–37% at room temperature or up to 28% at 50°C. This reaction leads to products of large range of epoxide contents and characterized by absence of side-ring opening groups, proved by IR and ¹H-NMR analysis. By infrared spectroscopy it was demonstrated a good correlation between the absorbances of the residual double bonds and of the epoxide groups versus the epoxide content in the range from 0 to approx. 60 mol % level. The solubility and gel content were studied in various solvents, demonstrating that epoxidation leads to increasing gel content at high epoxide levels and to enhancing sensitivity of the product toward polar solvents. By GPC, it was shown for the soluble fraction that epoxidation was accompanied by reducing the molecular weight and by change of the MWD compared with the original NR.     

Electrically conducting compound synthesized from lignin and sulfur

Summary A thermostable polymer, called sulfur lignin, has been obtained when modifying lignin by reactions with elemental sulfur at elevated temperatures. Sulfur linkages are formed between the phenylpropane units of lignin in these reactions. The conductivity of polymers which have a conjugated structure can be increased by doping with electron acceptors or donors. The conductivity of sulfur lignin has been measured after doping with various dopants and from the results it is concluded that the doped sulfur lignin has the properties off a semi conductive polymer.     

Investigation of corrosion behaviors in chloride solutions of G-X 10CrNiMoNb 18-10 austenitic stainless steel produced by different casting techniques

In this study, corrosion resistance of G-X 10CrNiMoNb 18–10 austenitic stainless steel parts, which had been produced through sand molded casting and centrifugal casting methods, and exposed to two-step heat treatments and cooled in different mediums (water, oil, air and oven), in 3.5% NaCl solution were examined according to weight loss, potentiodynamic polarization and impedance spectroscopy. According to the obtained results, it was found that corrosion rate of G-X 10CrNiMoNb 18–10 austenitic stainless steel, which had been cast through the sand molded casting method, heated up to the 1^st stage (1065–1120°C), and then cooled in the air, the lowest.